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Advanced microstructural analysis of ferrite materials by means of electron backscatter diffraction (EBSD)
NASA Astrophysics Data System (ADS)
The analysis of the achieved texture is of great importance for the performance of ferrite materials, either bulk or thin films. The recently developed electron backscatter diffraction (EBSD) technique enables a spatially resolved study of the crystallographic orientations by means of recording of Kikuchi patterns. To our knowledge, such a thorough EBSD analysis was not yet performed in any oxidic magnetic material, and only very recently on magnetite thin films by us. A good surface polishing/cleaning is essential for this analysis, as the method requires an undisturbed surface area for a high image quality (IQ). This information is recorded to each measured Kikuchi pattern, together with a parameter describing the quality of indexation. Here, the spatially highly resolved EBSD mappings provide additional information as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, an analysis of the grain aspect ratio is possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.
Koblischka-Veneva, A.; Koblischka, M. R.; M³cklich, F.
An automated method of quantifying ferrite microstructures using electron backscatter diffraction (EBSD) data.
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, Gwķnaļlle; Ringer, Simon P; Cairney, Julie M
Phase Identification of Individual Crystalline Particles by Electron Backscatter Diffraction (EBSD)
Recently, an EBSD system was developed that uses a 1024 x 1024 CCD camera coupled to a thin phosphor. This camera has been shown to produce excellent EBSD patterns. In this system, crystallographic information is determined from the EBSD pattern and coupled with the elemental information from energy or wavelength dispersive x-ray spectrometry. Identification of the crystalline phase of a sample is then made through a link to a commercial diffraction database. To date, this system has been applied almost exclusively to conventional, bulk samples that have been polished to a flat surface. In this investigation, the authors report on the application of the EBSD system to the phase identification analysis (PIA) of individual micrometer and submicrometer particles rather than flat surfaces.
Application of electron backscatter diffraction (EBSD) to fracture studies of ferritic steels.
The application of electron backscatter diffraction (EBSD) to fracture studies has provided a new method for investigating the crystallography of fracture surfaces. The crystallographic indices of cleavage planes can be measured both directly from the fracture surface and indirectly from metallographic sections perpendicular to the plane of the adjoining fracture surfaces. The results of direct individual cleavage facet plane orientation measurements are presented for carbon-manganese (C-Mn) and low-alloy Mn-Mo-Ni (similar to ASTM A553 type-B). Pressure vessel steel weld metals, obtained from fracture surfaces of Charpy impact test specimens fractured at various test temperatures and for an ultra-low carbon steel (Fe-0.002C- 0.058P) fractured at -196 degrees C by impact. In addition to the direct measurement from the fracture surface, cleavage facet orientation measurements for the ultra-low carbon steel were complemented by the results obtained from the metallographic sections. Fractographic observations revealed that cleavage fracture is accommodated by a microvoid coalescence fracture micromechanism, which was induced by decohesion of second phase particles (inclusions). The correlation between the direct and indirect methodologies shows that the cleavage facet planes are dominated by the [001] plane orientations, and indicated that even when information concerning the full five degrees of freedom is inaccessible, the cleavage facet plane could still be determined. Finally, the advantages and disadvantages of direct orientation measurements from the fracture surface and indirectly by a destructive sectioning technique are discussed. PMID:11996192
Davies, P A; Novovic, M; Randle, V; Bowen, P
Texture analysis of melt-spun Ni-Mn-Ga tapes by means of electron backscatter diffraction (EBSD)
NASA Astrophysics Data System (ADS)
A texture analysis is performed by means of the electron-backscatter diffraction technique (EBSD) on melt-spun ribbon-like samples of the composition Ni52.5Mn24.5Ga23 (at.-%) were prepared. A dedicated surface treatment is required in order to achieve high quality Kikuchi patterns. For this purpose, mechanical polishing plus ion polishing was employed. EBSD analysis and transmission electron microscopy revealed that the samples have a polycrystalline, granular morphology, with grain sizes around 1 - 2 ?m. Several larger grains being present in the region selected for EBSD analysis, and many small grains are found, even embedded in the larger ones. The larger grains exhibit a common direction of elongation, yielding to a specific texture.
Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Mitra, A.; Panda, A. K.
Characterization of pyramidal inversion boundaries in Sb2O3-doped ZnO by using electron back-scattered diffraction (EBSD).
The composition planes of the inversion boundary induced by the addition of Sb2O3 to ZnO ceramics were analyzed crystallographically by the application of electron back-scattered diffraction (EBSD) analysis and stereographic projection techniques. The inversion boundary was determined to consist of three discrete composition planes, {0001}, {1011}, {1010}. PMID:17435286
Jo, Wook; Park, Chan; Kim, Doh-Yeon
Study of ferrous corrosion products on iron archaeological objects by electron backscattered diffraction (EBSD)
NASA Astrophysics Data System (ADS)
The corrosion of iron-based archaeomaterials in anoxic environments leads mainly to Fe(II) compounds, like the hydroxychloride ?-Fe2(OH)3Cl, chukanovite Fe2(OH)2CO3 or siderite FeCO3. The understanding of the mechanisms then necessarily implies a thorough investigation of the chemical, mechanical and morphological characteristics of the Fe(II)-based layer that develops between the metal surface and the environment. In the peculiar case of Fe(II) compounds, generally very reactive towards O2, the main concern is to prevent any transformation by air during the analysis. The EBSD technique is adapted on a scanning electron microscope (SEM) where the samples are analysed under vacuum and consequently sheltered from air. Different options offered by EBSD for phase characterisation and microstructural study were tested for the first time on the rust layers of two archaeological iron nails. Results were confronted to those obtained by micro-Raman spectroscopy, which was used as reference method. Magnetite, Fe(II) hydroxychloride ?-Fe2(OH)3Cl and siderite were analysed successfully but improvements have to be brought for the study of other compounds such as iron oxyhydroxides and chukanovite. The choice of experimental parameters in our approach as well as the potentialities and limits of the technique for this kind of application are discussed.
Azoulay, Ilanith; Conforto, Egle; Refait, Philippe; Rķmazeilles, Cķline
Grain-scale processes in actively deforming magma mushes: New insights from electron backscatter diffraction (EBSD) analysis of biotite schlieren in the Jizera granite, Bohemian Massif
In the porphyritic Jizera granite, Bohemian Massif, three distinct types of lattice-preferred orientations of biotite grains were revealed in schlieren-delineated magmatic structures using the electron backscatter diffraction (EBSD) method. (1) Biotite basal planes (001) reorient from schlieren-subparallel near the schlieren base to schlieren-perpendicular in the upper part of the schlieren. Both orientations share subhorizontal ?N¢S to ?NNE¢SSW-trending a axes. (2)
Ji?Ē Äßk; Krystof Verner; Patricie T²covß
Application of Electron Backscattered Diffraction (EBSD) and Atomic Force Microscopy (AFM) to Determine Texture, Microtexture, and Grain Boundary Energies in Ceramics
Crystallographic orientations in alumina (Al203) and magnesium aluminate spinel (MgAl204) were obtained using electron backscattered diffraction (EBSD) patterns. The texture and mesotexture (grain boundary misorientations) were random and no special boundaries were observed. The relative grain boundary energies were determined by thermal groove geometries using atomic force microscopy (AFM) to identify relationships between the grain boundary energies and misorientations.
Glass, S.J.; Rohrer, G.S.; Saylor, D.M.; Vedula, V.R.
Investigation of the microstructure of the Al¢Si eutectic in binary aluminium¢7 wt% silicon alloys by electron backscatter diffraction (EBSD)
Binary aluminium¢7 wt% silicon alloys with and without strontium modification have been cast with a cooling rate of 0.2¢0.6░C\\/s. The level of impurities has been kept at a minimum. The crystallographic orientation of the dendritic and eutectic aluminium as well as the eutectic silicon has been studied using electron backscatter diffraction (EBSD). The crystallographic orientation of the aluminium within the
G. Heiberg; L. Arnberg
Texture analysis of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x tapes by electron backscatter diffraction (EBSD)
NASA Astrophysics Data System (ADS)
Using automated orientation imaging, the grain orientations and texture of monofilamentary, Ag-sheathed (Pb,Bi) 2Sr 2Ca 2Cu 3O x (Bi-2223) tape is analysed in detail by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase scans including Bi-2223, Bi 2Sr 2CaCu 2O x, Bi 2Sr 2CuO x, (Sr,Ca) 14Cu 24O 41 and Ag to be performed. Two areas are selected for the EBSD analysis, one close to the silver sheath, the other located in the center of the sample. The grain orientation maps are presented for each phase separately allowing a new insight into the microtexture of Ag-sheathed Bi-2223 tapes. Furthermore, the EBSD analysis provides the possibility for a misorientation angle analysis within each individual phase.
Koblischka-Veneva, A.; Koblischka, M. R.; Qu, T.; Han, Z.; M³cklich, F.
Rapid assessment of anisotropic surface dissolution processes using atomic force microscopy (AFM) and electron backscattered diffraction (EBSD): A corrosion study of polycrystalline alloy 22 in various acidic environments
NASA Astrophysics Data System (ADS)
We utilize atomic force microscopy (AFM) and electron backscattered diffraction (EBSD) to correlate crystallographic orientations with dissolution rates of polycrystalline alloy 22 surfaces exposed to hydrochloric, sulfuric and oxalic acids. Additionally, we utilize AFM to gain insight into the dissolution mechanism processes and to correlate the dissolution current with penetration depth. For all acids, the dissolution rates scale with the deviation of the angle with the surface normal from the (1 1 1) direction. In hydrochloric and oxalic acids, the alloy dissolution is approximately uniform across individual grains. In contrast, in sulfuric acid, the dissolution is inhibited at crystallographic step sites.
Gray, Jeremy
Seismic anisotropy of the Pelona Schist from electron backscatter diffraction (EBSD) measurements of crystal preferred orientations (CPOs)
NASA Astrophysics Data System (ADS)
Seismic Anisotropy of the mid to lower crust is difficult to measure in the field by seismologists. Using a scanning electron microscope (SEM) to obtain crystal preferred orientations (CPO's) of mineral grains from samples taken from this region allows us to calculate seismic anisotropy theoretically using published mineral elastic constants. Calculations are made according to methods described in Mainprice et. al. (1990). Polished thin sections from the Pelona Schist were analyzed using electron back scatter diffraction (EBSD) in an SEM. The slide was tilted 70 degrees from horizontal. The samples included: 4 mica schists that were cut parallel to foliation, 3 corresponding mica schists cut perpendicular to foliation, and 2 xenoliths with high amphibole content. The 4 mica schists had max Vp's that ranged from 6.44 to 7.26 km/s; Vp anisotropies that ranged from 4.8% to 29.2%; and max Vs anisotropies from 7.0% to 42.6%. The 3 corresponding mica schists had max Vp's that ranged from 6.26 to 6.61 km/s; Vp anisotropies from 3.1% to 7.9%; and Vs anisotropies from 4.9% to 6.61%. In samples that were cut orthogonal to foliation biotite is difficult to index using the automated indexing routine and had to be found manually to improve calculations. This may account for significant differences in anisotropy between corresponding samples. The xenoliths had max Vp's of 6.14 and 6.48 km/s; their Vp anisotropies were both 6.5%; and their Vs anisotropies were 8.35 and 8.37. Our calculations give slightly higher maximum Vp than the average Vp reported in Pellerin and Christensen (1997) for similar rock types from the area. Calculated anisotropies are comparable to Pellerin and Christensen (1997). Samples with large amounts of mica had the highest anisotropy. On average, the calculated velocities have approximately hexagonal symmetry with a unique slow axis. In contrast, one sample contained significant plagioclase that caused velocities to be fast perpendicular to foliation. An assumption of hexagonal symmetry with a unique slow axis is a valid assumption for the Pelona Schist.
Wagner, K. C.; Brownlee, S. J.; Hacker, B. R.
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
Strain Determination Using Electron Backscatter Diffraction
In the present paper we demonstrate the use of electron backscatter diffraction (EBSD) for high resolution elastic strain determination. Here, we focus on analysis methods based on determination of small shifts in EBSD pattern with respect to a reference pattern using cross-correlation algorithms. Additionally we highlight the excellent spatial and depth resolution of EBSD and introduce the use of simulated diffraction patterns based on dynamical diffraction theory for sensitivity estimation. Moreover the potential of EBSD for strain analysis of strained thin films with particular emphasis on appropriate target preparation which respect to occurring lattice defects is demonstrated.
Krause, M.; Graff, A.; Altmann, F. [Fraunhofer Institute for Mechanics of Materials, Walter-Huelse-Str.1, 06120 Halle (Germany)
Grain-scale processes in actively deforming magma mushes: New insights from electron backscatter diffraction (EBSD) analysis of biotite schlieren in the Jizera granite, Bohemian Massif
NASA Astrophysics Data System (ADS)
In the porphyritic Jizera granite, Bohemian Massif, three distinct types of lattice-preferred orientations of biotite grains were revealed in schlieren-delineated magmatic structures using the electron backscatter diffraction (EBSD) method. (1) Biotite basal planes (001) reorient from schlieren-subparallel near the schlieren base to schlieren-perpendicular in the upper part of the schlieren. Both orientations share subhorizontal śN-S to śNNE-SSW-trending a axes. (2) In some domains, the a axes are steep and at a high angle to the schlieren plane while the c axes plunge shallowly and rotate around an ill-defined a axis. (3) In other domains, the EBSD coincides with background magnetic fabric of the host granite revealed using the anisotropy of magnetic susceptibility (AMS) method: that is, the a axes plunge shallowly to the SE or NW while the c axes are subhorizontal and cluster around the śNE-SW trend. These multiple biotite orientations in the schlieren are interpreted to reflect (1) velocity-gradient in laminar magma flow along channel-like conduits, localized within the high-strength host phenocryst framework, (2) grain-scale gravity-driven constrictional deformation of the magma mush, and (3) overprinting background (tectonic?) deformation transmitted across large parts of the magma chamber prior to its final crystallization. The grain-scale mechanisms of biotite fabric acquisition in the schlieren presumably involved rotation of biotite crystals during flow, with the biotite alignment reflecting the flow geometry and kinematics, replaced after flow cessation by melt-aided grain-boundary sliding of those biotite crystals still enclosed in melt pockets within otherwise static, highly crystallized magma mush. The latter process was sufficient to reorient biotite grains but not to cause destruction of the schlieren. Using the Jizera granite as a case example, we argue that the lattice-preferred orientation of mineral grains in mafic schlieren is highly sensitive to reorient in response to processes both associated with the schlieren formation (e.g., localized magma flow) and those that occur later and are superimposed onto the effectively solid, high-strength magma mush.
Äßk, Ji?Ē; Verner, KryÜtof; T²covß, Patricie
Electron Backscatter Diffraction in Low Vacuum Conditions
Most current scanning electron microscopes (SEMs) have the ability to analyze samples in a low vacuum mode, whereby a partial pressure of water vapor is introduced into the SEM chamber, allowing the characterization of nonconductive samples without any special preparation. Although the presence of water vapor in the chamber degrades electron backscatter diffraction (EBSD) patterns, the potential of this setup for EBSD characterization of nonconductive samples is immense. In this chapter we discuss the requirements, advantages and limitations of low vacuum EBSD (LV-EBSD), and present how this technique can be applied to a two-phase ceramic composite as well as hydrated biominerals as specific examples of when LV-EBSD can be invaluable.
El-Dasher, B S; Torres, S G
Electron backscatter diffraction: Strategies for reliable data acquisition and processing
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: email@example.com [Materials Research Centre, School of Engineering, Swansea University, Swansea SA2 8PP (United Kingdom)
Defining Electron Backscatter Diffraction Resolution
Automated electron backscatter diffraction (EBSD) mapping systems have existed for more than 10 years [1,2], and due to their versatility in characterizing multiple aspects of microstructure, they have become an important tool in microscale crystallographic studies. Their increasingly widespread use however raises questions about their accuracy in both determining crystallographic orientations, as well as ensuring that the orientation information is spatially correct. The issue of orientation accuracy (as defined by angular resolution) has been addressed previously [3-5]. While the resolution of EBSD systems is typically quoted to be on the order of 1{sup o}, it has been shown that by increasing the pattern quality via acquisition parameter adjustment, the angular resolution can be improved to sub-degree levels. Ultimately, the resolution is dependent on how it is identified. In some cases it can be identified as the orientation relative to a known absolute, in others as the misorientation between nearest neighbor points in a scan. Naturally, the resulting values can be significantly different. Therefore, a consistent and universal definition of resolution that can be applied to characterize any EBSD system is necessary, and is the focus of the current study. In this work, a Phillips (FEI) XL-40 FEGSEM coupled to a TexSEM Laboratories OIM system was used. The pattern capturing hardware consisted of both a 512 by 512 pixel SIT CCD camera and a 1300 by 1030 pixel Peltier cooled CCD camera. Automated scans of various sizes, each consisting of 2500 points, were performed on a commercial-grade single crystal silicon wafer used for angular resolution measurements. To adequately quantify angular resolution for all possible EBSD applications we define two angular values. The first is {omega}{sub center}, the mean of the misorientation angle distribution between all scan points and the scan point coincident to the calibration source (typically the scan center). The {omega}{sub center} value is used to describe the overall system resolution, as it effectively quantifies the deviation of all orientations in the scan relative to the diffraction pattern least affected by distortions. The second is {omega}{sub max}, the largest misorientation angle possible between any pair of points in the dataset, and describes the worst possible case. Fig. 1 shows the effects of scan size and captured pattern resolution (bin size) on both angular values, illustrating that smaller scan and bin sizes have the effect of increasing angular resolution. However, it can be observed that the benefits of utilizing smaller bin sizes (and consequently slower data collection) diminish with scan size. Fig. 2 shows the effect of the number of pixels used in the Hough transform (defined as the ratio of pixels used to maximum possible pixels) on the angular values. It can be seen that the best angular resolutions are achieved at a pixel ratio of 0.80, again illustrating that the use of higher resolutions is not always beneficial. As evidenced by the results, the use of {omega}{sub center} and {omega}{sub max} not only permits the characterization of the angular resolution of an EBSD system, but they allow for a more efficient utilization of the system by identifying appropriate settings depending on the desired angular resolution [6].
El-Dasher, B S; Rollett, A D
Eutectic solidification in hypoeutectic Al¢Si alloys: electron backscatter diffraction analysis
Nucleation and growth of the eutectic in hypoeutectic Al¢Si foundry alloys has been investigated by the electron backscatter diffraction (EBSD) mapping technique using a scanning electron microscope (SEM). Sample preparation procedures for optimizing mapping have been developed. To obtain a sufficiently smooth surface from a cast Al¢Si eutectic microstructure for EBSD mapping, an appropriate preparation technique by ion milling was
K Nogita; A. K Dahle
Recent developments in two fundamental aspects of electron backscatter diffraction
NASA Astrophysics Data System (ADS)
Two very different aspects of electron backscatter diffraction (EBSD) are considered in this paper. Firstly, the use of the technique for the measurement of grain size is discussed with particular reference to the development of international standards to help ensure reproducible and repeatable measurements. In particular the lessons learnt for both calibration of the complete SEM-EBSD system and in choice of the correct data acquisition and processing parameters from an international round robin are summarized. Secondly, extending the capability of EBSD through development of new detectors is discussed. New shadow casting methods provide a means to achieve better accuracy in definition of sample-pattern geometry, while increased detail can be obtained by larger cameras and ultimately direct electron detection.
Mingard, K. P.; Day, A. P.; Quested, P. N.
Electron backscatter diffraction of plutonium-gallium alloys
At Los Alamos National Laboratory a recent experimental technique has been developed to characterize reactive metals, including plutonium arid cerium, using electron backscatter diffraction (EBSD). Microstructural characterization of plutonium and its alloys by EBSD had been previously elusive primarily because of the extreme toxicity and rapid surface oxidation rate associated with plutonium metal. The experimental techniques, which included ion-sputtering the metal surface using a scanning auger microprobe (SAM) followed by vacuum transfer of the sample from the SAM to the scanning electron microscope (SEM), used to obtain electron backscatter diffraction Kikuchi patterns (EBSPs) and orientation maps for plutonium-gallium alloys are described and the initial microstructural observations based on the analysis are discussed. Combining the SEM and EBSD observations, the phase transformation behavior between the {delta} and {var_epsilon} structures was explained. This demonstrated sample preparation and characterization technique is expected to be a powerful means to further understand phase transformation behavior, orientation relationships, and texlure in the complicated plutonium alloy systems.
Boehlert, C. J. (Carl J.); Zocco, T. G. (Thomas G.); Schulze, R. K. (Roland K.); Mitchell, J. N. (Jeremy N.); Pereyra, R. A. (Ramiro A.)
Electron backscatter diffraction of MgB2
NASA Astrophysics Data System (ADS)
MgB2 is one of important new functional materials, which can play significant role in emerging Hydrogen Economy. If adopted, Hydrogen Economy would be a low-CO2 fossil-fuels-free answer to the current and future energy demands. To contribute to this economy, advanced methods of MgB2 preparation and an insight into its properties are required. This paper reports electron backscatter diffraction (EBSD) of dense polycrystalline MgB2 prepared by Hot Isostatic Pressing and Resistive Sintering. The EBSD study was performed in combination with polarised optical microscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy and scanning conductivity probe microscopy. The superconducting properties were measured in order to select specimens with highest critical current density to associate this density with structural features of the samples. The investigation shows importance of twist grain boundaries in increasing critical current density in MgB2.
Mikheenko, P.
Electron back-scattered diffraction of crystallized vanadium dioxide thin films on amorphous silicon dioxide
Crystalline films and isolated particles of vanadium dioxide (VO2) were obtained through solid phase crystallization of amorphous vanadium oxide thin films sputtered on silicon dioxide. Electron back-scattered diffraction (EBSD) was used to study the crystals obtained in the thin films, to differentiate them from different vanadium oxide stoichiometries that may have formed during the annealing process, and to study their
Felipe Rivera; Laurel Burk; Robert Davis; Richard Vanfleet
Many-beam dynamical simulation of electron backscatter diffraction patterns.
We present an approach for the simulation of complete electron backscatter diffraction (EBSD) patterns where the relative intensity distributions in the patterns are accurately reproduced. The Bloch wave theory is applied to describe the electron diffraction process. For the simulation of experimental patterns with a large field of view, a large number of reflecting planes has to be taken into account. This is made possible by the Bethe perturbation of weak reflections. Very good agreement is obtained for simulated and experimental patterns of gallium nitride GaN{0001} at 20kV electron energy. Experimental features like zone-axis fine structure and higher-order Laue zone rings are accurately reproduced. We discuss the influence of the diffraction of the incident beam in our experiment. PMID:17126489
Winkelmann, Aimo; Trager-Cowan, Carol; Sweeney, Francis; Day, Austin P; Parbrook, Peter
Exploring Spatial Resolution in Electron Back-Scattered Diffraction Experiments via Monte Carlo Simulation
A Monte Carlo model was used to simulate specimen-electron beam interactions relevant to electron back-scattered diffraction (EBSD). Electron trajectories were calculated for a variety of likely experimental conditions to examine the interaction volume of the incident electrons as well as that of the subset of incident electrons that emerge from the specimen, i.e., back-scattered electrons (BSEs). The spatial resolution of EBSD was investigated as functions of both materials properties, such as atomic number, atomic weight, and density, and experimental parameters, such as specimen thickness, tilt, and incident beam accelerating voltage. These simulations reveal that the achievable spatial resolution in EBSD is determined by these intrinsic and extrinsic parameters. PMID:9524142
Ren; Kenik; Alexander; Goyal
Application of electron backscatter diffraction techniques to quenched and partitioned steels.
Electron backscatter diffraction (EBSD) techniques were used to characterize "hot-rolled" quenched and partitioned microstructures produced via Gleeble thermal simulations representing a hot-strip cooling practice for steel. In particular, EBSD was utilized to positively identify the morphology and location of retained austenite, to qualitatively distinguish martensite from ferrite, and in an attempt to identify transition carbides. Large pools of retained austenite and some thin films were accurately indexed; however, there was some disparity between austenite volume fractions measured by EBSD and those measured by X-ray diffraction. Due to similarities between the crystal structures of martensite and ferrite (body centered tetragonal versus body centered cubic, respectively), martensite could not be distinguished from ferrite by indexing of diffraction patterns; however, martensite could qualitatively be distinguished from ferrite by regions of low image quality based on the very high dislocation density of martensite. PMID:21281538
Thomas, Grant; Speer, John; Matlock, David; Michael, Joseph
Electron backscatter diffraction characterization of laser-induced periodic surface structures on nickel surface
NASA Astrophysics Data System (ADS)
We report on the structural investigation of laser-induced periodic surface structures (LIPSS) generated in polycrystalline nickel target after multi-shot irradiation by femtosecond laser pulses. Electron backscatter diffraction (EBSD) is used to reveal lattice rotation caused by dislocation storage during LIPSS formation. Localized crystallographic damages in the LIPSS are detected from both surface and cross-sectional EBSD studies. A surface region (up to 200 nm) with 1-3░ grain disorientation is observed in localized areas from the cross-section of the LIPSS. The distribution of the local disorientation is inhomogeneous across the LIPSS and the subsurface region.
Sedao, Xxx; Maurice, Claire; Garrelie, Florence; Colombier, Jean-Philippe; Reynaud, Stķphanie; Quey, Romain; Blanc, Gilles; Pigeon, Florent
Investigation of microstructure of bulk Ni 2MnGa alloy by means of electron backscatter diffraction analysis
NASA Astrophysics Data System (ADS)
The microstructure of bulk samples of the shape memory alloy Ni 2MnGa is evaluated by means of electron backscatter diffraction (EBSD). The crystallographic orientation of individual grains can be determined with a high spatial resolution using an automated recording of Kikuchi patterns. The obtained data are presented in form of image quality (IQ) and orientation maps, pole figures and orientation distribution functions. Local EBSD maps and pole figures reveal details about the orientation of the twin structure. The twin structure is clearly resolved within the EBSD mappings; the matrix is oriented in [1 0 0] direction and there is a 90░ misorientation to the neighboring twin. Furthermore, pole figures obtained by EBSD are compared to those determined by means of X-ray texture analysis. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis.
Koblischka-Veneva, A.; Gachot, C.; Leibenguth, P.; M³cklich, F.
Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction
The grain boundary crystallographic misorientations of magnetic-pulse-welded (MPW) aluminum alloy (AA) 6061-T6 in linear and tubular configurations were examined using the electron backscattered diffraction (EBSD) technique. A refined structure of heavily deformed grains with higher grain boundary angles was observed in linear welds. Significant spalling was observed away from the joints, in the interior of tubular welds. The results show the complex interaction of shock waves with the materials during this impact welding process.
Zhang, Yuan [Ohio State University; Babu, Suresh [Ohio State University; Zhang, P [Edison Welding Institute; Kenik, Edward A [ORNL; Daehn, Glenn [Ohio State University
Misorientation mapping for visualization of plastic deformation via electron back-scattered diffraction.
The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data. PMID:17481344
Brewer, L N; Othon, M A; Young, L M; Angeliu, T M
Electron backscatter diffraction study of polycrystalline YBa 2Cu 3O 7- ? ceramics
NASA Astrophysics Data System (ADS)
The electron backscatter diffraction (EBSD) technique was applied to polycrystalline YBa 2Cu 3O 7- ? ceramics. To obtain good quality EBSD Kikuchi patterns on the ceramic superconductors, a new sample polishing route was established. Samples with and without KClO 3-doping were investigated; and the crystallographic orientations of the grains were analyzed using pole figures and EBSD orientation mapping. On the polycrystalline KClO 3-doped YBa 2Cu 3O 7- ? samples we found two major orientations (0 0 1) and (1 0 0) normal to the sample surface, while the undoped sample did not exhibit any orientation maxima. We ascribe this observation to the effect of a liquid phase due to the KClO 3-additive during the preparation process.
Koblischka-Veneva, Anjela; Koblischka, Michael R.; Simon, Petra; M³cklich, Frank; Murakami, Masato
Misorientations in [001] magnetite thin films studied by electron backscatter diffraction and magnetic force microscopy
NASA Astrophysics Data System (ADS)
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 patterns was achieved enabling multiphase scans and high spatial resolution measurements. Upon annealing in air, the magnetic properties of the magnetite thin films were found to change considerably. Using the EBSD analysis, we find that misoriented grains remaining after the annealing step form small islands with a size of about 100 nm. The size and distribution of these islands correspond well to the observations of antiferromagnetic pinning centers within the magnetic domain structures carried out by magnetic force microscopy on the same samples.
Koblischka-Veneva, A.; Koblischka, M. R.; Wei, J. D.; Zhou, Y.; Murphy, S.; M³cklich, F.; Hartmann, U.; Shvets, I. V.
Polymineralic orientation analysis of magmatic rocks using Electron BackScatter Diffraction: Implications for igneous fabric origin and evolution
Electron Back-Scatter Diffraction (EBSD), which provides an easy way of acquiring large numbers of individual crystallographic orientation data from different phases, has been applied to the study of magmatic fabrics. Using this technique, the crystallographic preferred orientation (CPO) of plagioclase, biotite, orthopyroxene, hornblende and quartz in natural tonalites and quartzdiorites (from the Santa Olalla Igneous Complex, SW Iberia) deformed during
I. Romeo; R. Capote; R. Lunar; N. Cayzer
Use of electropolishing for enhanced metallic specimen preparation for electron backscatter diffraction analysis
The effects of mechanical polishing with Al{sub 2}O{sub 3} and colloidal SiO{sub 2} followed by electropolishing were studied for preparation of metal alloy specimens for Electron Backscatter Diffraction (EBSD). The alloys studied were Inconel 718, a commonly used nickel-based superalloy, and a Ti-Al-Nb alloy (nominally Ti-22Al-28Nb(at.%)). Atomic Force Microscopy was used to measure the surface topography to attempt to correlate nano-scale surface roughness with EBSD pattern quality. The results suggest that mechanically polishing with Al{sub 2}O{sub 3} followed by electropolishing for a short time can produce EBSD pattern confidence indices and image quality values that are equal to or better than those produced by mechanically polishing with colloidal SiO{sub 2} alone. The data suggests that surface roughness on the scale considered here has much less effect on EBSD pattern quality than had been previously believed. The data suggests that removing the surface damage is more critical than reduction of topography for EBSD.
Wynick, G.L. [Alfred University, School of Engineering, Alfred, NY 14802 (United States); Boehlert, C.J. [Michigan State University, Department of Chemical Engineering and Materials Science, East Lansing, MI 48824-1226 (United States)]. E-mail: firstname.lastname@example.com
Combined application of electron backscatter diffraction and stereo-photogrammetry in fractography studies.
The main aim of this paper is to report on recent experimental developments that have succeeded in combining electron back-scatter diffraction (EBSD) with stereo-photogrammetry, compared with two other methods for study of fracture surfaces, namely visual fractography analysis in the scanning electron microscope (SEM) and EBSD directly from facets. These approaches will be illustrated with data relating to the cleavage plane orientation analysis in a ferritic and C-Mn steel. It is demonstrated that the combined use of EBSD and stereo-photogrammetry represents a significant advance in the methodology for facet crystallography analysis. The results of point counting from fractograph characterization determined that the proportions of intergranular fracture in C-Mn and ferritic steels were 10.4% and 9.4%, respectively. The crystallographic orientation was determined directly from the fracture surface of a ferritic steel sample and produced an orientation distribution with a clear trend towards the [001] plane. A stereo-photogrammetry technique was validated using the known geometry of a Vickers hardness indent. The technique was then successfully employed to measure the macroscopic orientation of individual cleavage facets in the same reference frame as the EBSD measurements. Correlating the results of these measurements indicated that the actual crystallographic orientation of every cleavage facet identified in the steel specimens is [001]. PMID:11580810
Davies, P A; Randle, V
Behavior of (1 1 1) grains during the thermal treatment of copper film studied in situ by electron back-scatter diffraction
An annealed Cu blanket film was investigated in situ at high temperature using electron back-scatter diffraction (EBSD). The primary aim of the experiment was to study the changes in the (111) texture in the Cu film where the microstructure was already stabilized by previous annealing treatment. Two separate investigations were carried out at the same location of the film for
Kabir-kumar Mirpuri; Horst Wendrock; Klaus Wetzig; Jerzy Szpunar
Electron Backscatter Diffraction of CdTe Thin Films: Effects of CdCl2 Treatment
In this work, the authors describe procedures to prepare the surface of close-spaced sublimation CdTe thin films necessary for producing good electron backscatter diffraction (EBSD) data. They found that polishing resulted in an amorphous layer on the surface and no Kikuchi pattern; however, ion-beam milling produced a relatively flat and good-quality surface, resulting in high-quality patterns and, consequently, excellent EBSD data. The authors used a combination of polishing and ion-beam milling or etching to study the crystalline structure of the CdTe film at different depths. They also used EBSD, in conjunction with other analytical techniques, to investigate the effects of the CdCl{sub 2} treatment, performed at different temperatures and times, on the recrystallization process of physical vapor deposition CdTe thin films. The authors found that the untreated films were <111> oriented, with grain sizes smaller than 1 {micro}m. The CdCl{sub 2} at 350 C produced partially recrystallized films, whereas treatments at 400 C or 420 C produced completely recrystallized films, with no texture, and grains with grain sizes varying from about 1 {micro}m to more than 40{micro}m. These films were so flat that good EBSD data could be obtained without any surface preparation. Atomic force microscopy and scanning electron microscopy showed that large grains had different morphologies than smaller grains, and EBSD showed that these large grains had <111> texture. These results indicate that the (111) surface is the lowest energy surface in these films and, consequently, <111>-oriented grains grow at the expense of grains oriented in less-favorable directions. Regardless of the deposition method and treatment, the CdTe films have a high density of 60{sup o} <111> twin boundaries.
Moutinho, H. R.; Dhere, R. G.; Romero, M. J.; Jiang, C.-S.; To, B.; Al-Jassim, M. M.
Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM
Naturally deformed ice contains subgrains with characteristic geometries that have recently been identified in etched surfaces using high-resolution light microscopy (LM). The probable slip systems responsible for these subgrain boundary types can be determined using electron backscattered diffraction (EBSD), providing the etch features imaged with reflected LM can be retained during EBSD data acquisition in a scanning electron microscope (SEM).
I. Weikusat; D. A. M. de Winter; G. M. Pennock; M. Hayles; C. T. W. M. Schneijdenberg; M. R. Drury
Assessing the precision of strain measurements using electron backscatter diffraction--part 1: detector assessment.
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 1ū1 binning is selected, are the primary reason for the observed increase in sensitivity at greater than 2ū2 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 1000ū1000 pixel image could be as low as 4.2ū10(-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
High temperature behavior of Cu films studied in-situ by Electron Backscatter Diffraction
Two different Cu films were studied in situ in FEG SEM as a function of temperature using electron back scatter diffraction (EBSD). Two different Cu films, one of which was partially recrystallized (film A) and the other annealed (film B) were investigated. Both EBSD and X-ray diffraction data showed that for film A there was a competition between the surface\\/interface
K. Mirpuri; H. Wendrock; S. Menzel; K. Wetzig; J. Szpunar
EBSD analysis of the microtexture of Ba-hexaferrite samples
NASA Astrophysics Data System (ADS)
The microtexture of differently prepared Ba-hexaferrite samples is investigated by means of electron backscatter diffraction (EBSD). Kikuchi patterns are obtained with a high image quality, enabling a spatial resolution of the EBSD maps of about 20 nm. The spatially highly resolved EBSD mappings provide additional information (individual grain orientation, misorientation angles, grain size distribution) as compared to the standard analysis techniques, which can contribute to an optimization of the growth process. Furthermore, as the crystallographic orientation of each grain is known, an exact analysis of the grain aspect ratio becomes possible which provides further insight to the microstructural dependence of the magnetic properties of ferrites.
Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Chen, Y.; Harris, V. G.
Electron backscatter diffraction analysis applied to [0 0 1] magnetite thin films grown on MgO substrates
NASA Astrophysics Data System (ADS)
Electron backscatter diffraction (EBSD) analysis is applied to [0 0 1] oriented magnetite thin films grown on MgO substrates. A high image quality of the Kikuchi patterns was achieved enabling multi-phase scans. Several types of magnetite thin films were analyzed; one as-grown and the others after different annealing steps in oxygen atmosphere. From the EBSD mappings, we learn that the optimum orientation in [0 0 1]-direction is not yet achieved for the as-grown sample, but develops upon oxygen treatment. Furthermore, the distribution of misorientation angles within the investigated area (=1 grain) is found to change during the annealing steps. After 3 min of annealing, most of the misorientations around 30░-40░ have vanished, and some islands with high misorientation angles remain, which may play a role as antiferromagnetic pinning centers.
Koblischka-Veneva, A.; Koblischka, M. R.; Zhou, Y.; Murphy, S.; M³cklich, F.; Hartmann, U.; Shvets, I. V.
Electron backscatter diffraction analysis of ZnO:Al thin films
NASA Astrophysics Data System (ADS)
Microstructural characterization and crystallographic orientation aspects of aluminium doped zinc oxide (ZnO:Al) thin films have been investigated by means of electron backscatter diffraction. ZnO:Al was produced by magnetron sputtering deposition from a ZnO ceramic target containing 2.0 wt% Al2O3 and 0.12 wt% Y2O3. Both top surface and cross-section analysis were performed. The experimental details concerning specific sample preparation procedures for EBSD investigations are presented. Crystalline texture was described by the inverse pole figure (IPF) maps. Strong texture on the basal plane orientation was observed on the analyzed thin film surface. In accordance with these results obtained from top surface investigations, a strong prismatic texture was found in cross-section analysis. From all these analyses a good description and quantification of the three dimensional configuration of the grains and of their crystallographic texture can be proposed.
Garcia, C. B.; Ariza, E.; Tavares, C. J.; Villechaise, P.
Electron backscatter diffraction of a Ge growth tip from a vertical gradient freeze furnace
NASA Astrophysics Data System (ADS)
The growth-tip region of a high-purity 4.2-cm-diameter Ge boule grown using low-pressure Bridgman methods in a vertical gradient freeze furnace was sectioned and polished in preparation for scanning electron microscopy and was characterized using electron backscatter diffraction (EBSD). The boule had a characteristic conical tip region with cone angle of 40░ of a right circular cylinder from which a section was taken along the boule longitudinal centerline with an approximate surface area of 4 cm 2. The majority of this surface area was characterized using EBSD and an image collage was assembled for the tip region. The grain structure, grain boundary orientation, twin structure, and overall crystal growth direction were determined. A crystal growth direction of approximately <1 1 2> was observed, which was also identified as the growth direction of several prominent twins observed in the tip region. The grain structure of the tip region appeared to be controlled by the sidewall nucleation of a stray grain that competed for dominance during growth. Grain boundaries and triple grain junctions were identified as low-energy coincident-site-lattice (CSL) boundaries and junctions of the ?3 and ?9 types.
Henager, Charles H., Jr.; Edwards, Danny J.; Schemer-Kohrn, Alan L.; Sundaram, S. K.; Riley, Brian J.; Bliss, Mary
Electron backscatter diffraction analysis of a CZT growth tip from a vertical gradient freeze furnace
NASA Astrophysics Data System (ADS)
Electron backscatter diffraction (EBSD) was used to characterize the growth-tip region of a 4.2-cm diameter CdZnTe (CZT) boule grown using low-pressure Bridgman method in a vertical gradient freeze furnace. The boule was sectioned and polished and a section taken along the boule longitudinal centerline with an approximate surface area of 1-cm 2 was used for optical and scanning electron microscopy. A collage was assembled using EBSD/SEM images to show morphological features, e.g., twin structure, grain structure, and overall crystal growth direction. Severely twinned regions originating from the tip and side walls were observed. The overall growth orientation was close to <1 1 0> and <1 1 2> directions. In some regions, the (0 0 1) poles of the CZT matrix aligned with the growth direction, while twins aligned such that (1 1 1) and (1 1 2) poles aligned with the growth direction. In some other areas, (1 1 2) or (0 1 1) poles of the CZT matrix aligned with the growth direction. New relationships between the CZT matrix and large Te polycrystalline particles were revealed: {1 1 2»} CZT??{1 1» 0 0} Te and {0 0 1} CZT??{0 1» 1» 1} Te.
Sundaram, S. K.; Henager, C. H.; Edwards, D. J.; Schemer-Kohrn, A. L.; Bliss, M.; Riley, B. R.
Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies
Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of special and random grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to elucidate these fundamental mechanisms. This investigation provides evidence that grain boundary network engineering and the formation of annealing twins disrupt the connectivity of the random grain boundary network and is likely responsible for the experimentally observed improvement in properties. This work illustrates that coupling of automated EBSD with other microstructural probes such as TEM and AFM provides data of greater value than any single technique in isolation. The coupled techniques have been applied to aid in understanding the underlying mechanisms of grain boundary network engineering and the corrosion properties of individual boundaries.
Schwartz, A.J.; Kumar, M.; Bedrossian, P.J.; King, W.E.
Position-dependent texture analysis of melt-textured YBCO by means of electron backscatter diffraction
NASA Astrophysics Data System (ADS)
The texture and phase distribution of melt-textured YBa 2Cu 3O x (YBCO) was studied by means of automated electron backscatter diffraction (EBSD) analysis as a function of the position in the bulk pellet of 4 cm diameter. A total of five samples was cut from the pellet; four samples from the surface of the bulk with different distances to the seed crystal, and one cut in vertical direction in the middle of the pellet. The melt-textured YBCO samples require a two-phase analysis to be performed, so a high surface quality is necessary to enable an automated EBSD scan. Good quality Kikuchi patterns are obtained from both the 1 2 3 and 2 1 1 phases. We found an inhomogeneous distribution of the 2 1 1 particles. Whereas the samples cut from the surface contain a large amount of 2 1 1 particles, in the samples of the vertical direction only traces of 2 1 1 particles are found. Furthermore, we measured the misorientation angle distribution of all samples. The data are presented in form of phase mappings, misorientation distribution functions and pole figures.
Koblischka-Veneva, A.; Koblischka, M. R.; Ogasawara, K.; Murakami, M.
Application of electron backscatter diffraction to bulk high-Tc superconductors
NASA Astrophysics Data System (ADS)
We have successfully obtained electron backscatter diffraction (EBSD) Kikuchi patterns on various bulk high-Tc superconductors (polycrystalline KClO3-doped and undoped YBa2Cu3O7-? (YBCO), single crystalline YBCO and NdBa2Cu3O7-y) and on YBCO and NdBCO thin films. We have established a sample polishing procedure to obtain intense Kikuchi patterns without an additional carbon coating of the ceramic superconductors. We present Kikuchi patterns, pole figures and orientation maps of the samples. On the polycrystalline KClO3-doped YBCO samples we find two major orientations (001) and (100) normal to the sample surface, while the undoped sample does not exhibit any orientation maxima, which is ascribed to the effect of a liquid phase due to the KClO3-additive during the preparation process. Furthermore, we discuss the future possibilities for the application of the EBSD technique for growing larger, bulk melt-textured samples for applications.
Koblischka-Veneva, A.; Koblischka, M. R.; Simon, P.; M³cklich, F.; Murakami, M.
EBSD analysis of electroplated magnetite thin films
NASA Astrophysics Data System (ADS)
By means of electron backscatter diffraction (EBSD), we analyse the crystallographic orientation of electroplated magnetite thin films on Si/copper substrates. Varying the voltage during the electroplating procedure, the resulting surface properties are differing considerably. While a high voltage produces larger but individual grains on the surface, the surfaces become smoother on decreasing voltage. Good quality Kikuchi patterns could be obtained from all samples; even on individual grains, where the surface and the edges could be measured. The spatial resolution of the EBSD measurement could be increased to about 10 nm; thus enabling a detailed analysis of single magnetite grains. The thin film samples are polycrystalline and do not exhibit a preferred orientation. EBSD reveals that the grain size changes depending on the processing conditions, while the detected misorientation angles stay similar.
Koblischka-Veneva, A.; Koblischka, M. R.; Teng, C. L.; Ryan, M. P.; Hartmann, U.; M³cklich, F.
EBSD study on YBCO textured bulk samples: correlation between crystal growth and 'microtexture'
This work describes an electron backscattered diffraction (EBSD) study of the perovskite-derived structures YBa2Cu3O7-delta. After having pointed out the difficulties of EBSD analyses in resolving the orientations of these pseudo-cubic structures, various YBaCuO bulk samples are analysed and the correlation between the microstructure, crystal growth and global texture, determined by neutron diffraction, is carried out. Homogeneous 'microtexture' with small subdomain
D. Grossin; C. Henrist; J.-Ph Mathieu; S. Meslin; C. Harnois; J.-G. Noudem; R. Cloots; D. Chateigner
Study of grain boundary properties in Ag-clad Bi2Sr2Ca2Cu3Ox tapes by multi-phase electron backscatter diffraction analysis
NASA Astrophysics Data System (ADS)
The properties of grain boundaries within Ag-clad (Pb,Bi)2Sr2Ca2Cu3Ox (Bi-2223) tapes are studied by means of electron backscatter diffraction (EBSD). The achieved high image quality of the Kikuchi patterns enables multi-phase EBSD scans including Bi-2223, Bi2Sr2CaCu2Ox (Bi-2212), Bi2Sr2CuOx (Bi-2201), (Sr,Ca)14Cu24O41 and Ag to be performed. For the EBSD scans a maximum spatial resolution of 30 nm was reached enabling a detailed orientation analysis. The nature of the grain boundaries is discussed on the base of the EBSD data. While the main orientation of the tape is in [0 0 1] direction, a large number of misorientations is detected. These misorientations are visualized using crystal direction (CD) maps. Furthermore, EBSD enables the spatially resolved mapping of the misorientation angles within each phase separately. The influence of these grain boundaries on the current transport properties is discussed.
Koblischka-Veneva, A.; Koblischka, M. R.
Characterization of bulk superconductors through EBSD methods
NASA Astrophysics Data System (ADS)
The application of electron backscatter diffraction (EBSD) technique to bulk high- Tc superconductors is presented and reviewed. Due to the ceramic nature and the complex crystallographic unit cells of the perovskite-type high- Tc superconductors, the EBSD analysis is not yet as common as it deserves. We have successfully performed EBSD analysis on a variety of high- Tc compounds and samples including polycrystalline YBCO (pure and doped by alkali metals), melt-textured YBCO, thin and thick films of YBCO; the ōgreen phaseö Y 2BaCuO 5, thin film and melt-textured NdBa 2Cu 3O x and Bi-2212 single crystals and tapes. It is shown that the surface preparation of the samples is crucial due to the small information depth (up to 100 nm) of the EBSD technique. High quality Kikuchi patterns are the requirement in order to enable the automated EBSD mapping, which yields phase distributions, individual grain orientations and the misorientation angle distribution. The results can be presented in form of mappings, as charts, and as pole figures. These informations are required for a better understanding of the growth mechanism(s) of bulk high- Tc superconductors intended for applications.
Koblischka, M. R.; Koblischka-Veneva, A.
A novel approach for site-specific atom probe specimen preparation by focused ion beam and transmission electron backscatter diffraction.
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
Dihedral corner reflector backscatter using higher order reflections and diffractions
NASA Technical Reports Server (NTRS)
The uniform theory of diffraction (UTD) plus an imposed edge diffraction extension is used to predict the backscatter cross sections of dihedral corner reflectors which have right, obtuse, and acute included angles. The UTD allows individual backscattering mechanisms of the dihedral corner reflectors to be identified and provides good agreement with experimental cross-section measurements in the azimuthal plane. Multiply reflected and diffracted fields of up to third-order are included in the analysis for both horizontal and vertical polarizations. The coefficients of the uniform theory of diffraction revert to those of the geometrical theory of diffraction (GTD) in far-field cross-section analyses, but finite cross sections can be obtained everywhere by considering mutual cancellation of diffractions from parallel edges. Analytic calculations are performed using UTD coefficients; hence the accuracy required in angular measurements is more critical as the distance increases. The common far-field approximation that all rays to the observation point are parallel is too gross an approxiation for the angular parameters in the UTD coefficients in the far field.
Griesser, Timothy; Balanis, Constantine A.
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.
Interactions of Y2BaCuO5 particles and the YBCO matrix within melt-textured YBCO samples studied by means of electron backscatter diffraction
NASA Astrophysics Data System (ADS)
By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y2BaCuO5(211) particles within melt-textured YBa2Cu3Ox (YBCO) samples. On both components, we obtained high-quality Kikuchi patterns, thus allowing the automated mapping of the crystal orientations and a two-phase analysis of the samples. Investigations were performed on a variety of melt-textured YBCO samples. In melt-textured YBCO with (001) orientation, we find that the embedded 211 particles do not have any preferred orientation. The EBSD maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. From the obtained EBSD mappings, we can conclude that the formation of small 211 particles will not disturb the YBCO matrix growth, whereas the presence of large 211 particles causes severe changes in the YBCO growth, leading to the formation of subgrains. The EBSD results are presented in the form of local orientation maps and local pole figures.
Koblischka-Veneva, A.; Koblischka, M. R.; M³cklich, F.; Ogasawara, K.; Murakami, M.
Application of Electron Backscatter Diffraction to Phase Identification
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
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.
Plastic strain characterization in austenitic stainless steels and nickel alloys by electron backscatter diffraction
NASA Astrophysics Data System (ADS)
Stress corrosion cracking (SCC) is enhanced by cold work and causes many problems in components of the nuclear power plants. Besides, during manufacturing, installation, welding and service of the material, residual strains can be produced increasing the susceptibility to SCC. For this reason, it is important to characterize the degree of plastic strain due to dislocation accumulation in each crystal. Electron backscatter diffraction (EBSD), in conjunction with scanning electron microscope (SEM), has been a great advance in this field because it enables to estimate the plastic strain in a quick and easy way. Nevertheless, over the last few years, a lot of different mathematical expressions to estimate the plastic strain have appeared in the literature. This situation hinders the election of one of them by a novel scientist in this field. Therefore, in this paper some of the more common expressions used in the calculation of the angular misorientation have been presented and discussed in order to clarify their more important aspects. Then, using one of these expressions (average local misorientation), curves relating misorientation density with known levels of strain will be obtained for an austenitic stainless steel 304L and nickel base alloy 690, which have shown a linear behaviour that is in good agreement with results found in the literature. Finally, using curves obtained in previous steps, levels of plastic strain in a plate of nickel base alloy 600 welded with weld metal 182 were estimated between 8 and 10% for a high temperature mill annealing sample.
Sßez-Maderuelo, A.; Castro, L.; de Diego, G.
Electron Backscattered Diffraction Analysis Of Narrow Copper Interconnects In Cross-View To Investigate Scale Effect On Microstructure
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)
An electron backscatter diffraction investigation of crystallographic orientations of embedded nanoparticles within melt-textured YBCO high temperature superconductors
NASA Astrophysics Data System (ADS)
Microstructures of melt-textured YBCO samples with embedded nanosized particles of Y2BaCuO5 (Y-211) and Y2Ba4CuMOx (M-2411 with M = U,Zr) are analysed by means of electron backscatter diffraction (EBSD). With the recent developments of the EBSD technique, we can directly measure the crystallographic orientation of the embedded nanoparticles, employing a spatial resolution of about 40 nm. The high image quality of the Kikuchi patterns allows true three-phase (YBCO, Y-211 and M-2411) scans to be performed. The Y-211 particles do not exhibit any preferred orientation, even if their size is considerably reduced, to the 100 nm range. The size reduction reduces the negative influence of the Y-211 particles on the YBCO matrix, however. U-2411 particles, which are formed during the processing stage, do not show any orientation, and with increasing concentration, some texture develops. In contrast to this, embedded Zr-2411 particles are fully oriented in the (001) orientation according to the surrounding superconducting matrix.
Koblischka-Veneva, A.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Shlyk, L.; Krabbes, G.
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
EBSD study of hydrogen-induced cracking in API5 LX46 pipeline steel
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. Gonzßlez; T. Baudin; J. M. Hallen; R. Penelle
Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells
Electron backscatter diffraction (EBSD) provides information on the crystallographic structure of a sample, while scanning Kelvin probe microscopy (SKPM) provides information on its electrical properties. The advantage of these techniques is their high spatial resolution, which cannot be attained with any other techniques. However, because these techniques analyze the top layers of the sample, surface or cross section features directly influence the results of the measurements, and sample preparation is a main step in the analysis. In this work we investigated different methods to prepare cross sections of CdTe/CdS solar cells for EBSD and SKPM analyses. We observed that procedures used to prepare surfaces for EBSD are not suitable to prepare cross sections, and we were able to develop a process using polishing and ion-beam milling. This process resulted in very good results and allowed us to reveal important aspects of the cross section of the CdTe films. For SKPM, polishing and a light ion-beam milling resulted in cross sections that provided good data. We were able to observe the depletion region on the CdTe film and the p-n junction as well as the interdiffusion layer between CdTe and CdS. However, preparing good-quality cross sections for SKPM is not a reproducible process, and artifacts are often observed.
Moutinho, H. R.; Dhere, R. G.; Jiang, C. S.; Al-Jassim, M. M.
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
Magnetic domain structure and crystallographic orientation of electrical steels revealed by a forescatter detector and electron backscatter diffraction.
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
Microtexture of magnetite thin films of (001) and (111) orientations on MgO substrates studied by electron-backscatter diffraction
NASA Astrophysics Data System (ADS)
The grain orientation of (001)- and (111)-oriented magnetite thin films grown on MgO substrates (film thickness of 100-400 nm) is analyzed by means of the electron-backscatter diffraction (EBSD) technique. The (001) surface after a short annealing in air (1 min, 250 ░C) is characterized by the presence of tiny (diameter of 100-200 nm) misoriented islands, which have an influence on the antiferromagnetic coupling within the film. In the (111)-oriented films, such defects are found to be absent, and the films show a very homogeneous surface. The achieved spatial resolution enables further a cross-section analysis of a 400-nm-thick film with (001) orientation, even close to the interface MgO-magnetite.
Koblischka-Veneva, A.; Koblischka, M. R.; Murphy, S.; Arora, S. K.; M³cklich, F.; Hartmann, U.; Shvets, I. V.
Zirconium deformation behavior: insights from EBSD measurements.
The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.
Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.); Gray, G. T. (George T.), III
Detrital quartz and quartz cement in Upper Triassic reservoir sandstones of the Sichuan basin: Characteristics and mechanisms of formation based on cathodoluminescence and electron backscatter diffraction analysis
NASA Astrophysics Data System (ADS)
The relationship between detrital quartz grains and silica cement is significant because cement is often a major cause of porosity reduction in oil and gas reservoirs, thus degrading hydrocarbon reservoir quality. On the other hand, the attributes of grain surfaces may inhibit cementation, thus preserving porosity in the reservoirs. In this study we focus on the microstructures in quartz grains and secondary overgrowths (quartz cement) in the heavily cemented sandstones from uplifted Upper Triassic siliciclastic rocks in the southern Sichuan basin, China. Electron backscatter diffraction (EBSD), optical, and cathodoluminescence (CL) imaging methods have been used to address the microstructural and crystallographic attributes of the detrital grains and their overgrowths. This study confirms that: (1) the overgrowth zones of quartz are clearly visible in optical and CL images; (2) all silica overgrowths are perfectly crystalline quartz; (3) quartz cements have a syntaxial relationship with the host detrital grain, indicating crystallographic continuity between the detrital quartz and its overgrowth; and (4) crystallographic maps confirm that Dauphinķ twins commonly occur both in the detrital grains and in the quartz cement. Most Dauphinķ twins are developed at grain-grain contacts, including the margins of detrital grains where they are in contact with quartz cement. Some twins are limited to a single grain, whereas others cross grain-cement boundaries. Based on these twin distributions, we can distinguish inherited twins from twins that formed during/after burial compaction. This study documents the grain deformation structures induced by sedimentary compaction, and these structures can be accurately illustrated by EBSD data.
Zhang, Bo; Zhang, Jinjiang; Yan, Shuyu; Gu, Zhidong; Wang, Xiaoxian
Using a controlled pressure field emission gun scanning electron microscope to acquire EBSD data on non-conductive samples
NASA Astrophysics Data System (ADS)
The present work is dealing with electron backscattered diffraction. It is well known that EBSD requires most of the time and up to now, both an important high voltage and a large beam current. However, in such conditions, acquiring EBSD maps on non-conductive samples require to either coat the sample with a conductive thin layer or to use a controlled pressure SEM and then introduce some gas in the sample chamber. The idea here is to present some data comparisons between both solutions. Patterns, orientation images and simulations were carried out to try to access meaningful quantitative results.
Brisset, F.
Diffraction-controlled backscattering threshold and application to Raman gap
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)
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.
Grain orientations and distribution of Y2Ba4CuUOx phase in melt-textured YBCO with addition of depleted uranium oxide studied by EBSD
NASA Astrophysics Data System (ADS)
The local grain orientations and the distribution of Y2Ba4CuUOx (U-2411) phase are measured within melt-textured YBCO samples by means of electron backscatter diffraction (EBSD). In this work, several samples with varying addition (0.1-0.8 wt%) of depleted uranium oxide (DU) were analysed by means of EBSD. The embedded U-2411 particles were found to have sizes around 200 nm, some large particles being present in the samples with a high DU concentration. Combined EBSD and EDX analysis enabled the identification of the Kikuchi patterns of the U-2411 phase, so that a true three-phase EBSD scan (YBCO, Y2BaCuO5 and U-2411) becomes possible.
Koblischka-Veneva, A.; M³cklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Murakami, M.
Effect of the surface preparation techniques on the EBSD analysis of a friction stir welded AA1100-B{sub 4}C metal matrix composite
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: email@example.com [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)
EBSD characterization of dendrite growth directions, texture and misorientations in hot-dipped Al¢Zn¢Si coatings
Al¢Zn¢Si coatings (55% Al¢43.4% Zn¢1.6% Si in weight pct) deposited on steel substrates by the hot-dipping process have been analyzed by Electron Back-Scattered Diffraction (EBSD) and optical microscopy. In these 20?m-tick films, the main growth directions of the dendrites have been unambiguously identified as being the closest to directions. When the surface precisely corresponds to a (001) plane of the
A Sķmoroz; Y Durandet; M Rappaz
Evaluation of macrozone dimensions by ultrasound and EBSD techniques
Titanium alloys are known to have texture heterogeneities, i.e. regions much larger than the grain dimensions, where the local orientation distribution of the grains differs from one region to the next. The electron backscattering diffraction (EBSD) technique is the method of choice to characterize these macro regions, which are called macrozones. Qualitatively, the images obtained by EBSD show that these macrozones may be larger or smaller, elongated or equiaxed. However, often no well-defined boundaries are observed between the macrozones and it is very hard to obtain objective and quantitative estimates of the macrozone dimensions from these data. In the present work, we present a novel, non-destructive ultrasonic technique that provides objective and quantitative characteristic dimensions of the macrozones. The obtained dimensions are based on the spatial autocorrelation function of fluctuations in the sound velocity. Thus, a pragmatic definition of macrozone dimensions naturally arises from the ultrasonic measurement. This paper has three objectives: 1) to disclose the novel, non-destructive ultrasonic technique to measure macrozone dimensions, 2) to propose a quantitative and objective definition of macrozone dimensions adapted to and arising from the ultrasonic measurement, and which is also applicable to the orientation data obtained by EBSD, and 3) to compare the macrozone dimensions obtained using the two techniques on two samples of the near-alpha titanium alloy IMI834. In addition, it was observed that macrozones may present a semi-periodical arrangement. - Highlights: Black-Right-Pointing-Pointer Discloses a novel, ultrasonic NDT technique to measure macrozone dimensions Black-Right-Pointing-Pointer Proposes a quantitative and objective definition of macrozone dimensions Black-Right-Pointing-Pointer Compares macrozone dimensions obtained using EBSD and ultrasonics on 2 Ti samples Black-Right-Pointing-Pointer Observes that macrozones may have a semi-periodical arrangement.
Moreau, Andre, E-mail: email@example.com [National Research Council of Canada, 75 de Mortagne Blvd. Boucherville, QC, Canada J4B 6Y4 (Canada)] [National Research Council of Canada, 75 de Mortagne Blvd. Boucherville, QC, Canada J4B 6Y4 (Canada); Toubal, Lotfi [National Research Council of Canada, 75 de Mortagne Blvd. Boucherville, QC, Canada J4B 6Y4 (Canada) [National Research Council of Canada, 75 de Mortagne Blvd. Boucherville, QC, Canada J4B 6Y4 (Canada); Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, QC, Canada H3C 1K3 (Canada); Bocher, Philippe [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, QC, Canada H3C 1K3 (Canada)] [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, QC, Canada H3C 1K3 (Canada); Humbert, Michel; Uta, Elena; Gey, Nathalie [Laboratoire d'Etude des Microstructures et de Mecanique des Materiaux (LEM3), UMR CNRS 7239, Universite de Lorraine, Ile du Saulcy, 57045 METZ Cedex 1 (France)] [Laboratoire d'Etude des Microstructures et de Mecanique des Materiaux (LEM3), UMR CNRS 7239, Universite de Lorraine, Ile du Saulcy, 57045 METZ Cedex 1 (France)
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
Microstructural evolution in adiabatic shear bands of copper at high strain rates: Electron backscatter diffraction characterization
The microstructural evolution of adiabatic shear bands in annealed copper with different large strains at high strain rates has been investigated by electron backscatter diffraction. The results show that mechanical twinning can occur with minimal contribution to shear localization under dynamic loading. Elongated ultrafine grains with widths of 100-300 nm are observed during the evolution of the adiabatic shear bands. A rotational dynamic recrystallization mechanism is proposed to explain the formation of the elongated ultrafine grains. - Highlights: Black-Right-Pointing-Pointer The microstructural evolution of ASB is studied by electron backscatter diffraction. Black-Right-Pointing-Pointer Twinning can occur in ASB while the contribution to shear localization is slight. Black-Right-Pointing-Pointer Elongated ultrafine grains are observed during the evolution process of ASB. Black-Right-Pointing-Pointer A possible mechanism is proposed to explain the microstructure evolution of ASB.
Tang Lin [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Chen Zhiyong, E-mail: email@example.com [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Zhan Congkun; Yang Xuyue; Liu Chuming [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Cai Hongnian [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)
Electron backscattering diffraction analysis of an ancient wootz steel blade from central India
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: firstname.lastname@example.com; 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)
Study of grain morphology of various magnetite samples by means of EBSD
NASA Astrophysics Data System (ADS)
(001)- and (111)-oriented magnetite thin films were grown on MgO substrates (film thickness 200 nm) by means of oxygen-plasma-assisted molecular beam epitaxy and by laser-ablation. Further samples are electroplated magnetite thin films on Si/copper substrates and films from biogenic magnetite. The achieved grain orientations are analysed by means of the electron backscatter diffraction (EBSD) technique. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution of up to 40 nm on such ceramic materials. A high image quality of the recorded Kikuchi patterns was achieved enabling multi-phase scans (e.g., Fe3O4, MgO, Fe2O3). The facets of individual grains are analysed in detail.
Koblischka-Veneva, A.; Koblischka, M. R.
Characterization of nano-composite M-2411/Y-123 thin films by electron backscatter diffraction and in-field critical current measurements
NASA Astrophysics Data System (ADS)
Thin films of nano-composite Y-Ba-Cu-O (YBCO) superconductors containing nano-sized, non-superconducting particles of Y2Ba4CuMOx (M-2411 with M = Ag and Nb) have been prepared by the PLD technique. Electron backscatter diffraction (EBSD) has been used to analyze the crystallographic orientation of nano-particles embedded in the film microstructure. The superconducting YBa2Cu3O7 (Y-123) phase matrix is textured with a dominant (001) orientation for all samples, whereas the M-2411 phase exhibits a random orientation. Angular critical current measurements at various temperature (T) and applied magnetic field (B) have been performed on thin films containing different concentration of the M-2411 second phase. An increase in critical current density Jc at T < 77 K and B < 6 T is observed for samples with low concentration of the second phase (2 mol % M-2411). Films containing 5 mol % Ag-2411 exhibit lower Jc than pure Y-123 thin films at all fields and temperatures. Samples with 5 mol % Nb-2411 show higher Jc(B) than phase pure Y-123 thin films for T < 77 K.
Bodea, M. A.; Pedarnig, J. D.; Withnell, T. D.; Weber, H. W.; Cardwell, D. A.; Babu, N. Hari; Koblischka-Veneva, A.
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
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.
Crystallographic analysis of grain boundary Bcc-precipitates in a Ni¢Cr alloy by FESEM\\/EBSD and TEM\\/Kikuchi line methods
Variant selection of intergranular bcc-Cr precipitates in a Ni¢43mass% Cr alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FESEM) and Kikuchi line analysis in transmission electron microscope (TEM). A single variant was invariably selected at the underlying grain boundaries (GB) when GB-precipitates were KS-related with respect to both the
Yoshitaka Adachi; Kazunari Hakata; Kaneaki Tsuzaki
Identification of dynamic ferrite formed during the deformation of super-cooled austenite by image-based analysis of an EBSD map
Differentiation of dynamically and statically transformed ferrites in SIDT (Strain-Induced Dynamic Transformation) steel was\\u000a carried out by various image-based analyses of EBSD (Electron BackScattered Diffraction) maps. Various identification methods\\u000a were tried on the basis on the grain size, and the intra- and inter-granular misorientations. The grain-size-based method\\u000a was valid only when a bimodal grain size distribution in the ferrite phase,
Yong Min Kim; Tae-Hong Ahn; Kwang Kyun Park; Kyu Hwan Oh; Heung Nam Han
Backscatter analysis of dihedral corner reflectors using physical optics and the physical theory of diffraction
NASA Technical Reports Server (NTRS)
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 reflected wave and reduce the complexity of the analysis. In the second method, PO is used at almost every reflection in order to maximize the accuracy of the PTD solution at the expense of a rapid increase in complexity. Induced surface current densities and resulting cross section patterns are illustrated for the two methods.
Griesser, Timothy; Balanis, Constantine A.
Mapping of femtosecond laser-induced collateral damage by electron backscatter diffraction
NASA Astrophysics Data System (ADS)
The distribution of the collateral damage beneath craters produced by ultrafast (femtosecond) laser single pulses in a nickel base superalloy single crystal has been analyzed using electron backscatter diffraction. The procedure is based on measurements of the localized crystal rotations caused by the dislocations generated by the shock wave that is produced as an effect of laser pulse interaction with a material. Damage in the form of lattice misorientation created by excess dislocations was negligible at laser fluences up to 2 J/cm2. At higher fluences (5.1-41 J/cm2), the depth of the damage zone beneath the crater increased linearly with laser fluence. Based on lattice misorientation, excess dislocation densities as high as 3 ū 1010/cm2 are calculated to be present below the ablated surface in the high fluence regime.
Kumar, Anish; Pollock, Tresa M.
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.
Crystallographic analysis of plate martensite in Fe-28.5 at.% Ni by FE-SEM/EBSD
Crystallographic analysis of plate martensite in an Fe-28.5 at.% Ni alloy was studied by electron backscattering diffraction (EBSD) in a scanning electron microscope equipped with a field emission gun (FE-SEM). It was shown that sound orientation mapping was possible even for the martensite having a high density of lattice defects and the FE-SEM/EBSD could be a strong tool for crystallographic/microstructural analysis of martensite in steels. It was confirmed that the martensite in this alloy held the Nishiyama-Wassermann (N-W) orientation relationship. Variant analysis of every martensite crystal was successfully done from orientation mapping data. It was clarified that a certain rule of variant selection operated within local areas. The procedures of crystallographic analysis of N-W martensite were explained in detail.
Kitahara, Hiromoto [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)]. E-mail: email@example.com; Ueji, Rintaro [Department of Advanced Materials Science, Faculty of Engineering, Kagawa University, 2217-20 Hayashi-cho, Takamatsu 761-0396 (Japan); Ueda, Masato [Department of Materials Science and Processing, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Tsuji, Nobuhiro [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan); Minamino, Yoritoshi [Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871 (Japan)
Characterization of dual-phase steel microstructure by combined submicrometer EBSD and EPMA carbon measurements.
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
Calculation of Elastic Anisotropy Using Emats Validated by Ebsd in Rolled Aluminium Sheet
NASA Astrophysics Data System (ADS)
Determining the Orientation Distribution Function (ODF) accurately and quickly in a non-destructive manner has many benefits and applications within industry. The ODF is essentially a quantitative description of the existence of anisotropy, or texture, within a metal sheet. The anisotropy can be seen experimentally by the variation in Lamb wave velocities in the plane of the sheet as a function of angle to the Rolling Direction. The anisotropy can be quantitatively described by the Orientation Distribution Coefficients (ODCs) W400, W420 and W440. Electron Backscatter Diffraction (EBSD) is a technique performed in a SEM. It infers the crystallographic directions of crystals near-surface, and can be applied to a number of samples. It enables the accurate quantitative and qualitative description of microstructural properties such as grain size. By manipulating the Bunge-Euler angle data given by the EBSD technique, here we describe a method to extrapolate the effective elastic constants for Aluminium sheet, and go on to generate a method to predict a Lamb wave velocity profile as a function of angle in a directly comparable format to that measured using a commercially available EMAT-EMAT S0 Lamb wave velocity measurement system. Results show a very good correlation between the predicted velocity trace from EBSD compared to that measured ultrasonically, and hence the respective ODCs, except in the cases where surface to bulk texture inhomogeneity exist.
Essex, S. D.; Potter, M. D. G.; Dixon, S.
Boundary identification in EBSD data with a generalization of fast multiscale clustering.
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
Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM.
Naturally deformed ice contains subgrains with characteristic geometries that have recently been identified in etched surfaces using high-resolution light microscopy (LM). The probable slip systems responsible for these subgrain boundary types can be determined using electron backscattered diffraction (EBSD), providing the etch features imaged with reflected LM can be retained during EBSD data acquisition in a scanning electron microscope (SEM). Retention of the etch features requires that the ice surface is stable. Depending on the pressure and temperature, sublimation of ice can occur. The equilibrium temperature for a low pressure SEM operating at 1 ū 10(-6) hPa is about -112░C and operating at higher temperatures causes sublimation. Although charging of uncoated ice samples is reduced by sublimation, important information contained in the etch features are removed as the surface sublimes. We developed a method for collecting EBSD data on stable ice surfaces in a low pressure SEM. We found that operating at temperatures of <-112░C reduced sublimation so that the original etch surface features were retained. Charging, which occurred at low pressures (<1.5 ū 10(-6) to 2.8 ū 10(-5) hPa) was reduced by defocusing the beam. At very low pressures (<1.5 ū 10(-6) hPa) the spatial resolution with a defocused beam at 10 kV was about 3 ?m in the x-direction at -150░C and 0.5 ?m at -120░C, because at higher temperature charging was less and only a small defocus was needed to compensate it. Angular resolution was better than 0.7░ after orientation averaging. Excellent agreement was obtained between LM etch features and EBSD mapped microstructures. First results are shown, which indicate subgrain boundary types comprised of basal (tilt and twist) and nonbasal dislocations (tilt boundaries). PMID:21155992
Weikusat, I; DE Winter, D A M; Pennock, G M; Hayles, M; Schneijdenberg, C T W M; Drury, M R
Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements in naturally deformed eclogites
Observations of dislocations, sub-grains and elongated crystal shapes 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 and simple shear, we performed numerical simulations of CPO development during plastic flow using the visco-plastic self-consistent model. As input for the models we use
David Mainprice; Jķr¶me Bascou; Patrick Cordier; Andrķa Tommasi
Crystal preferred orientations of garnet: comparison between numerical simulations and electron back-scattered diffraction (EBSD) measurements in naturally deformed eclogites
NASA Astrophysics Data System (ADS)
Observations of dislocations, sub-grains and elongated crystal shapes 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 and simple shear, we performed numerical simulations of CPO development during plastic flow using the visco-plastic self-consistent model. As input for the models we use the slip systems determined by transmission electron microscopy using experimentally deformed specimens. Although in garnet 66 slip systems are available, slip on the <111>{110} system provides over 86% of the total strain in the simulations. Characteristic CPO distributions are produced for the three deformation paths, with the CPO being strongest for axial shortening and weakest for simple shear. Compared with low-symmetry minerals, the pole figure densities of garnet, which has cubic symmetry, are weak. <100> axes tend to align with the shortening direction in all three deformation modes. The simulations are compared with CPO of naturally deformed garnet from nine eclogite samples from the Alps, Norway, and Mali, which contain 20-40% garnet. All samples show weak garnet CPO. Only two samples have a CPO pattern similar to the simulations for simple shear, no samples are similar to simulations for axial strain or pure shear. The presence of other weaker minerals, such as omphacite and quartz, with volume fractions higher than garnet, probably prevented garnet from becoming highly strained and developing characteristic CPOs in these eclogites. Higher volume fractions of garnet and higher temperature conditions may, however, allow the development of garnet CPO in the mantle transition zone, particularly within subducted oceanic material (MORB).
Mainprice, David; Bascou, Jķr¶me; Cordier, Patrick; Tommasi, Andrķa
Texture and nano-scale internal microstructure of otoliths in the Atlantic molly, Poecilia mexicana: a high-resolution EBSD study.
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; G÷tz, A; Griesshaber, E; Plath, M; Schmahl, W W
Study of dynamic grain growth by electron microscopy and EBSD.
The effect of hot deformation on fully recrystallized aluminium-copper alloys (Al-4wt%Cu and Al-33wt%Cu) with different volume fractions of CuAl(2) has been studied. The alloys are Zener pinned systems with different superplastic properties. Strain-induced grain growth, observed in both alloys, was quantitatively estimated by means of electron microscopy and EBSD and compared with the rate of static grain growth. Surface marker observations and in situ hot-deformation experiments combined with EBSD were aimed at clarifying the mechanisms responsible for the changes in the deformed microstructures. A sequence of secondary and backscattered electron images and EBSD maps was obtained during in situ SEM deformation with different testing conditions. Overlaying EBSD maps for the Al-4wt%Cu with channelling contrast images showed that grain boundary motion occurred during deformation, creating a layered structure and leading to an increase in size of some grains and shrinkage of others. Of a particular interest are results related to behaviour of CuAl(2) in superplastic Al-33wt%Cu during deformation, including several problems with the use of EBSD in this alloy. PMID:19250464
Rofman, O V; Bate, P S; Brough, I; Humphreys, F J
Experimental study of corrosion behavior for burnished aluminum alloy by EWF, EBSD, EIS and Raman spectra
NASA Astrophysics Data System (ADS)
The effect of burnish process on 2024 aluminum alloy was studied by electron work function and electron backscattered diffraction (EBSD). Moreover, the corrosion resistance of thin passive films formed on 2024 aluminum alloy in borate buffer solutions was studied by the electrochemical impedance spectroscopy (EIS), the Mott-Schottky plots and the galvanostatic techniques. The composition of passive films was analyzed by Raman spectra. The results obtained indicated that the impedance increased due to burnish and this was attributed to decreased electron work function and higher current efficiency in the burnished aluminum alloy which led to thicker passive films. It was further supported by Raman spectra experiment. Moreover, the donor and acceptor concentration of passive films and their the semiconductor type have changed due to burnish.
Jinlong, Lv; Hongyun, Luo; Jinpeng, Xie
Assessing the precision of strain measurements using electron backscatter diffraction--part 2: experimental demonstration.
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 4ū4 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
EBSD for microstructure and property characterization of the SiC-coating in TRISO fuel particles
NASA Astrophysics Data System (ADS)
Tristructural-isotropic (TRISO)-coated particle fuel is being developed for use in the Next Generation Nuclear Plant. The reliable and precise characterization of the microstructure and properties of the SiC layer in the TRISO particle is essential for optimizing processing parameters to ensure reproducibility and performance of the coatings. Electron backscatter diffraction (EBSD) is a time-efficient analytical tool for obtaining a wealth of information on the SiC layer. In this study, we report the application of EBSD to the analysis of the SiC layer in a TRISO particle. The SiC layer identified as 3C-SiC with an average elastic stiffness of ś402 GPa was mainly composed of random boundaries with a small fraction of low-? CSLBs. A few large grains, which were generally associated with local strains and tended to be columnar with the long axis oriented approximately along the TRISO particle radial direction, were observed in the SiC layer with an increased population from the IPyC-SiC to the SiC-OPyC interfaces.
Tan, L.; Allen, T. R.; Hunn, J. D.; Miller, J. H.
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.
Morphological analyses of minute crystals by using stereo-photogrammetric scanning electron microscopy and electron back-scattered diffraction.
We present a new method for the morphological analyses of minute faceted crystals by combining stereo-photogrammetric analysis of scanning electron microscope images and electron back-scattered diffraction. Two scanning electron microscope images of the same crystal, recorded at different tilt angles of the specimen stage, are used to determine the orientations of crystal edges in a specimen-fixed coordinate system. The edge orientations are converted to the indices [uvw] in the crystal system using the crystal orientation determined by electron back-scattered diffraction analysis. The Miller indices of crystal facets are derived from the indices of the edges surrounding the facets. The method is applicable to very small crystal facets. The angular error, as derived from tests using a calcite crystal of known morphology, is a few degrees. To demonstrate the applicability of the method, the morphology of boehmite (gamma-AlOOH) precipitated from solution during the dissolution of anorthite was analyzed. The micrometre-sized boehmite crystals are surrounded by two {010} basal facets and eight equivalent side facets that can be indexed equally well as {323}, {434} or {545}. We suggest that these side facets are in fact {111}, the morphology having been modified slightly (by a few degrees) by a small extension associated with opening along (010) microcleavage planes. Tiny {140} facets are also commonly observed. PMID:18045330
Kameda, Jun; Inoguchi, Ryoichi; Prior, David J; Kogure, Toshihiro
EBSD Characterization of Dendrites in Synthetic and Natural Rocks
NASA Astrophysics Data System (ADS)
Arborescent crystals in igneous rocks are associated with extreme crystallization environments: the protoplanary disk (chondrules), Earth's ultramafic Archean mantle (komatiite), and terrestrial submarine-erupted lavas (pillow basalts), although the role of morphological instabilities in more mundane settings such as magma reservoirs of modern oceanic islands is increasingly appreciated (see Welsch et al., V16). Fundamentals of dendrite formation are presumably well understood: branching morphologies belie crystal growth conditions in which the driving force for solidification produces a kinetic roughening transition, transforming an atomically smooth crystal-liquid interface into a rough, adhesive interface capable of extremely rapid advancement. However, not since photomicrograhic advances made possible close observations of snow crystals (Nakaya 1936), has there been a more promising set of analytical tools to characterize dendrites in natural and synthetic materials in pursuit of new insights. We are investigating clinopyroxene (cpx) in the quenched top of Fe-rich tholeiitic lava (Munro Township, Northeast Ontario; Fig. 1) and a synthetic basalt of similar character (Hammer 2006) with electron backscatter diffraction (EBSD), 3D reconstruction of optical serial sections, and TEM. Here we report intriguing phenomena observed with EBSD common to both samples. Severe thinning of dendrite trunks and repeated tip splitting destroys the self-similarity associated with classical dendrites and instead presages 'seaweed' morphology. Split tips manifest incremental trajectory deflections, producing gently arched trunks (Fig. 1A) as well as tightly curved (r<10 um) trunks. Crystals progressively rotate clockwise about cpx <010>, producing distinctive misorientation maps and pole figures (Fig. 1C). Parallel branches exhibit similar rotational trajectories, carving parallel arcs in the <010> pole figure. The high incidence of side branching and tip splitting is consistent with very rapid growth velocity, associated with extremely high kinetic undercooling at the dendrite tip (Mullis and Cochrane 2001). A plausible explanation for development of the lattice misorientation is engulfment of impurity particles (possibly plagioclase), a process of progressive tip deflection that has been modeled using phase field theory (Grßnßsy et al. 2003). The ubiquity of cpx rotation in concert with seaweed morphology suggests that not only is growth exceptionally rapid, but profoundly influenced by heterophase effects. Nakaya, U et al. (1934-1938) Investigation on Snow. J Fac Sci Hokkaido Univ, Ser II, 1-2. Hammer, JE (2006) EPSL 248, 618-637. Mullis, AM and Cochrane RF (2001) Acta Mater 49, 2205-2214. Grßnßsy, L et al. (2003) Nature doi:10.1038/nmat815.
Hammer, J. E.; Tiley, J.; Shiveley, A.; Knox, S.; Viswanathan, G.
High resolution electron backscatter diffraction measurements of elastic strain variations in the presence of larger lattice rotations.
In this paper we explore methods of measuring elastic strain variations in the presence of larger lattice rotations (up to -11░) using high resolution electron backscatter diffraction. We have examined the fundamental equations which relate pattern shifts to the elastic strain tensor and modified them to a finite deformation framework from the original infinitesimal deformation one. We incorporate the traction free boundary condition into the minimisation problem for the finite deformation case (i.e. large rotations and small elastic strains). Numerical experiments show that this finite deformation kinematic analysis continues to work well, while the infinitesimal analysis fails, when the misorientation between test and reference pattern is made increasingly high. However, measurements on patterns simulated using dynamical diffraction theory indicated that this formulation is not sufficient to recover elastic strains accurately because the pattern shifts are not determined accurately when large rotations are present. To overcome this issue we remap the test pattern to an orientation that is close to that of reference pattern. This remapping was defined by a finite rotation matrix, which was estimated from the infinitesimal rotation matrix measured using cross-correlation. A second cross-correlation analysis between the reference pattern and the remapped test pattern allows the elastic strains to be recovered using the much simpler infinitesimal deformation theory. We have also demonstrated that accurate recovery of elastic strains requires accurate knowledge of the pattern centre if this remapping algorithm is used. PMID:22366635
Britton, T B; Wilkinson, A J
Fluvial suspended sediment characteristics by high-resolution, surrogate metrics of turbidity, laser-diffraction, acoustic backscatter, and acoustic attenuation
NASA Astrophysics Data System (ADS)
Sedimentation is a primary and growing environmental, engineering, and agricultural issue around the world. However, collection of the data needed to develop solutions to sedimentation issues has declined by about three-fourths since 1983. Suspended-sediment surrogates have the potential to obtain sediment data using methods that are more accurate, of higher spatial and temporal resolution, and with less manually intensive, costly, and hazardous methods. The improved quality of sediment data from high-resolution surrogates may inform improved understanding and solutions to sedimentation problems. The field experiments for this research include physical samples of suspended sediment collected concurrently with surrogate metrics from instruments including 1.2, 1.5, and 3.0 megahertz frequency acoustic doppler current profilers, a nephelometric turbidity sensor, and a laser-diffraction particle size analyzer. This comprehensive data set was collected over five storms in 2009 and 2010 at Yellow River near Atlanta, Georgia. Fluvial suspended sediment characteristics in this study can be determined by high-resolution surrogate parameters of turbidity, laser-diffraction and acoustics with model errors 33% to 49% lower than traditional methods using streamflow alone. Hysteresis in sediment-turbidity relations for single storm events was observed and quantitatively related to PSD changes of less than 10 microns in the fine silt to clay size range. Suspended sediment particle size detection (PSD) is significantly correlated with ratios of measured acoustic attenuation at different frequencies; however the data do not fit the theoretical relations. Using both relative acoustic backscatter (RB) and acoustic attenuation as explanatory variables results in a significantly improved model of suspended sediment compared with traditional sonar equations using only RB. High resolution PSD data from laser diffraction provide uniquely valuable information; however the size detection limits of the instrument is a significant limitation.
Landers, Mark Newton
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
Preparation of samples with both hard and soft phases for electron backscatter diffraction: examples from gold mineralization.
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
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
Application of EBSD method for the investigation of microstructure and crystallographic orientation in RE2Zr2O7 TBC
NASA Astrophysics Data System (ADS)
Modern aero engine turbine blades made of nickel-based superalloys are covered by thermal barrier coatings (TBC) for thermal and oxidation protection. A new generation of TBCs consist of a bond coat (thin layer of MCrAlY, where M may be Ni, Co, Fe) followed by a ceramic top coat of RE2Zr2O7 (RE - rare earth element). In this paper we present the possibility of the electron backscatter diffraction (EBSD) method for characterisation of the microstructure and crystallographic orientation of a new TBC consisting of a Gd2Zr2O7 top coat and a NiFeCrAlY bond coat after long thermal exposure (1100 ░C, 500 h). During thermal exposure, a thermally grown oxide (TGO) layer forms at the bond coat/top coat interface. The TGO is mainly composed of Al2O3. But, there is a possible reaction between Gd2Zr2O7 and Al2O3, leading to Gd-Al-O phases. Phase composition plays an important role in controlling the stress evolution, TGO deformation and crack propagation. Application of SEM-EDS-EBSD techniques allows direct characterisation of the chemical composition, phase composition and crystallographic orientation in the ceramic top coat and TGO layers. This paper presents the possibilities of using the EBSD method for phase identification (Gd2Zr2O7, spinel Ni(Al,Cr)2O4, GdAlO3 and other phases) and orientation analysis of grains in the TGO layer.
Chmiela, B.; Soza?ska, M.; Moskal, G.
EBSD analysis of the Shergottite Meteorites: New developments within the technique and their implication on what we know about the preferred orientation of Martian minerals
NASA Astrophysics Data System (ADS)
What we know about the geology and mineralogy of the Martian surface has been characterised by both the use of remote sensing techniques and the analysis of Martian meteorites. Various techniques are employed to conduct these analyses including crystallographic, geochemical and spectral measurements, all of which enable us to infer a geological history for these rocks. Several references have been made to the potential for preferred orientation of crystals within the Shergottites [1] and their implication for the cooling history of the respective magmas on Mars [2]. We have already shown that a preferred orientation of the two pyroxenes, augite and pigeonite, can be seen in the Zagami meteorite using electron back-scatter diffraction (EBSD) analysis [3]. However, when compared to previous modal studies of the same meteorites [4], it becomes apparent that the current EBSD datasets for Martian meteorites are incomplete. Indexing of some minerals can be hampered by the lack of available matches within library databases for EBSD, or become difficult to resolve between minerals where crystallographic differences between similar minerals fall below the technical limitations of the instrument [3]. Recent advances in EBSD technologies combined with the simultaneous acquisition of energy-dispersive spectra (EDS) however now allow us to determine a more comprehensive set of analyses in a much shorter period of time, fully resolving even similar minerals where areas have been left with no indexing previously [5]. Preliminary investigations suggest that the new technology can successfully index >90% of the sample. The most recent EBSD analyses potentially reveals previously unseen fabrics in the meteorites alongside the EDS hyper-spectral imaging helping to resolve any unknown or questionable phases within them. In this study we will present new data from an investigation using EDS alongside EBSD analysis on 2 Shergottite meteorites, SAU 005 and Zagami, to further resolve their constituent minerals and any existing preferred orientations. [1] Stolper E. and McSween, H.Y. Jnr (1979) Geochemica et Cosomochimica Acta, 43, 1475-1498 [2] McCoy, T.J. et al. (1992) Geochimica et Cosomochimica Acta, 56, 3571-3582 [3] N.R. Stephen et al. (2010) Abstract #5008 73rd Annual Meeting of the Meteoritical Society [4] N.R. Stephen et al. (2010) Abstract #2367 Lunar & Planetary Science Conference XLI [5] J. Berlin et al. (2011) Abstract #2723 Lunar & Planetary Science Conference XLII
Stephen, N.; Benedix, G. K.; Bland, P.; Berlin, J.; Salge, T.; Goran, D.
Energy-dispersive spectroscopy and electron backscatter diffraction analysis of isothermally aged SAF 2507 type superduplex stainless steel
NASA Astrophysics Data System (ADS)
Due to thermal effects, several precipitation and segregation processes are known in duplex stainless steels. These microstructural changes influence both of the original phases, but in different ways. Isothermal ageing in a large range of temperature was performed on SAF 2507 type steel. The temperature range was 300-1000 ░C, the ageing time was between 100 s and 24 h. This paper discusses the results of ageing at 900 ░C. Microstructural changes were investigated by electron microscopy, energy-dispersive spectroscopy and electron backscattered diffraction analysis. This technique allowed the determination of the microstructure of the secondary austenite and sigma phase and their mutual orientation properties. Beside this, thermoelectric power measurements were also performed, which gave information about the kinetics of the precipitation process. Results showed that sigma-phase precipitation started right after 200 s in the case of annealed steel, and faster than 100 s in the cold-rolled state. After 5000 s, the delta-ferrite disappeared. Chemical composition of sigma phase was independent on the ageing time. A small decrease in nickel content was observed with a slight increase of Cr content. Small amount of chi phase had also been observed on the ferrite-ferrite boundaries, but later they changed into sigma phase. Similarly to sigma phase, chi phase showed significant phosphorus enrichment. During ageing, small chrome nitride precipitates developed, which amount increased in time, and some vanadium could be measured in them. The orientation relationship between austenite and sigma phase deviated from Nenno-orientationship with about 24░, and seems to form a [110]?[310] relationship, which was characteristic right from the beginning of the process, and remains more or less constant.
Dobranszky, J.; Szabo, P. J.; Berecz, T.; Hrotko, V.; Portko, M.
An investigation into the use of electron back scattered diffraction to measure recrystallized fraction
The Electron Back-Scattered Diffraction (EBSD) technique is in its infancy and is a highly promising area of development. Use of EBSD has been predominantly for the determination of crystallographic textures. Other applications have also been considered, which include: crystal structure determination, phase determination, grain boundary studies and both elastic and plastic deformation measurement. Although it has been acknowledged that an important use of the EBSD could be in the measurement of recrystallization and its kinetics there are a number of inherent problems with such measurements using EBSD. These problems include the ability of the system to index deformed microstructures even those on a fine scale, the difficulties of analyzing patterns in the region of grain boundaries and the problems of sample preparation which is critical in the quality of the diffraction patterns obtained. The aim of the present study is to determine whether it is possible to measure the volume fraction recrystallized using EBSP of partially recrystallized stainless steel. This has been done by investigation of the quality of matching between the observed and calculated diffraction patterns, and the quality of the observed patterns measured in terms of their contrast. The material used was stainless steel 316L.
Black, M.P.; Higginson, R.L. (Univ. of Sheffield (United Kingdom). Dept. of Engineering Materials)
3D EBSD characterization of deformation structures in commercial purity aluminum
A method to map the microstructure in deformed aluminum in three dimensions is presented. The method employs serial sectioning by mechanical polishing, and electropolishing to obtain a good surface quality, and orientation mapping of individual grains in each section by electron backscattered diffraction. Techniques to carefully align the sample and to accurately measure the thickness of the material removed in each serial section are described. A new method for stacking the two dimensional maps together to produce a three dimensional visualization of the microstructure is presented. The data are analyzed in terms of the deformation-induced orientation spread within each grain. In particular the advantage of using three dimensional data, as opposed to two dimensional data, is illustrated, by inclusion of information about the three dimensional morphology of a grain and its neighbors. - Research Highlights: The deformation structures in commercial purity aluminum were characterized in 3D. The method employs serial sectioning by mechanical polishing, and electropolishing to obtain a good surface quality, and orientation mapping of individual grains in each section by electron backscattered diffraction. Techniques to carefully align the sample and to accurately measure the thickness of the material removed in each serial section are described. A new method for stacking the two dimensional maps together to produce a three dimensional visualization of the microstructure is presented. The data are analyzed in terms of the deformation-induced orientation spread within each grain. In particular the advantage of using three dimensional data, as opposed to two dimensional data, is illustrated, by inclusion of information about the three dimensional morphology of a grain and its neighbors. The highlights of the paper include: {yields} a method to obtain 3D EBSD data over a large volume {yields} a modified method for section alignment based on characteristics of deformed grains {yields}a critical comparison of information available from 2D and 3D investigations.
Lin, F.X., E-mail: firstname.lastname@example.com [Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark); Godfrey, A. [Laboratory of Advanced Materials, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Jensen, D. Juul; Winther, G. [Danish-Chinese Center for Nanometals, Materials Research Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark, DK-4000 Roskilde (Denmark)
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.
Phase Transformation Study in Nb-Mo Microalloyed Steels Using Dilatometry and EBSD Quantification
NASA Astrophysics Data System (ADS)
A complete microstructural characterization and phase transformation analysis has been performed for several Nb and Nb-Mo microalloyed low-carbon steels using electron backscattered diffraction (EBSD) and dilatometry tests. Compression thermomechanical schedules were designed resulting in the undeformed and deformed austenite structures before final transformation. The effects of microalloying additions and accumulated deformation were analyzed after CCT diagram development and microstructural quantification. The resulting microstructures ranged from polygonal ferrite and pearlite at slow cooling ranges, to a combination of quasipolygonal ferrite and granular ferrite for intermediate cooling rates, and finally, to bainitic ferrite with martensite for fast cooling rates. The addition of Mo promotes a shift in the CCT diagrams to lower transformation start temperatures. When the amount of Nb is increased, CCT diagrams show little variations for transformations from the undeformed austenite and higher initial transformation temperatures in the transformations from the deformed austenite. This different behavior is due to the effect of niobium on strain accumulation in austenite and its subsequent acceleration of transformation kinetics. This article shows the complex interactions between chemical composition, deformation, and the phases formed, as well as their effect on microstructural unit sizes and homogeneity.
Isasti, Nerea; Jorge-Badiola, Denis; Taheri, Mitra L.; Uranga, Pello
Orientations of Y 2BaCuO 5 and YBCO within melt-textured and directional solidified samples studied by EBSD
NASA Astrophysics Data System (ADS)
By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y 2BaCuO 5 (2 1 1) particles within melt-textured YBCO samples, and also the orientations of embedded YBCO particles in directional solidified 211 samples. On both systems, we obtained high-quality Kikuchi patterns, allowing the automated mapping of the crystal orientations and a multi-phase analysis. In melt-textured YBCO with (0 0 1) orientation, we find that the embedded 211 particles do not have any preferred orientation, but the maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. In directional solidified 211 samples, where the 211 is mainly oriented in (0 0 1) direction, the embedded YBCO particles show only some specific orientations.
Koblischka, M. R.; Koblischka-Veneva, A.; Reddy, E. S.; Schmitz, G. J.; Ogasawara, K.; Murakami, M.
Embedded Y 2Ba 4CuNbO x nanoparticles in melt-textured YBCO studied by means of EBSD
NASA Astrophysics Data System (ADS)
Melt-textured YBCO samples with embedded nanosize particles of Y 2Ba 4CuNbO x (Nb-2411) have been studied by means of electron backscatter diffraction (EBSD). The microstructure of these samples shows some distinct and unusual features, not observed in melt-textured bulk samples of other compositions. The resulting texture of the superconducting YBCO matrix is found to be excellent. Y 2BaCuO 5 (Y-211) particles, which are also present in these samples, exhibit no preferred orientation, as is the case generally in melt-textured YBCO samples. The embedded Y 2Ba 4CuNbO x particles, in contrast, exhibit only one orientation within the YBCO matrix. Furthermore, we find in the bulk pellets distinct areas with a high second phase particle concentration, adjacent to regions without secondary phase particles.
Koblischka-Veneva, A.; Koblischka, M. R.; Hari Babu, N.; Cardwell, D. A.; M³cklich, F.
Errors, Artifacts, and Improvements in EBSD Processing and Mapping
NASA Astrophysics Data System (ADS)
Electron back scatter diffraction (EBSD) mapping and indexing has rapidly come into widespread use. However, inadequate attention has been paid to the details of the method. Many of the algorithms in current use were chosen because they were the first ones that were found to work, rather than because they were optimum. Results of systematic study are presented. It is shown that more than one method can successfully correct a sampling artifact, that there is an optimum binning ratio, that Gaussian filtering provides an alternative to "butterfly convolution," that better alternatives for mapping image quality than those in current use are available, and that saving all the original patterns is practical and advantageous.
Tao, Xiaodong; Eades, Alwyn
Structural characterization of AlGaN\\/GaN superlattices by x-ray diffraction and Rutherford backscattering
We report on structural characterization of AlGaN\\/GaN superlattices grown on sapphire. The superlattice formation is evidenced by high-resolution x-ray diffraction and transmission electron microscopy. The high resolution x-ray diffraction spectra exhibit a pattern of satellite peaks. The in-plane lattice constants of the superlattices indicate the coherent growth of the AlGaN layer onto GaN. The average Al composition in the superlattices
Shengqiang Zhou; M. F. Wu; S. D. Yao; B. S. Zhang; H. Yang
Identification of magnetic Fe-Ti oxides in marine sediments by electron backscatter diffraction in scanning electron microscopy
In paleomagnetic and environmental magnetic studies the magnetomineralogical identification is usually based on a set of rock magnetic parameters, complemented by crystallographic and chemical information retrieved from X-ray diffraction (XRD), (electron) microscopy or energy dispersive spectroscopy (EDS) of selected samples. While very useful, each of these supplementary techniques has its limitations when applied to natural sample material which are related
C. Franke; G. M. Pennock; M. R. Drury; R. Engelmann; D. Lattard; J. F. L. Garming; T. von Dobeneck; M. J. Dekkers
Thermally-induced amphibole reaction rim development: EBSD insights into microlite orientation
NASA Astrophysics Data System (ADS)
Amphibole is an important mineral present in many calc-alkaline volcanic deposits. A hydrous phase, volcanic amphibole is only stable at pressures greater than 100 MPa (approx. 4 km), temperature less than ~860-870 oC, and in melts containing at least 4 wt % H2O. When removed from their thermal and barometric stability field, amphiboles decompose to form aggregate rims of anhydrous minerals. The thickness, texture, and mineralogy of these rims are thought to be reflective of the process driving amphibole disequilibrium (e.g. heating, decompression, etc). However, significant overlap in rim thicknesses and microlite textures means that distinguishing between processes it not simple. This study employed backscatter diffraction (EBSD) to examine both experimental heating-indced amphibole reaction rims and natural amphibole reaction rim from Augustine Volcano. We collected crystal orientation maps of amphibole reaction rims to investigate if different types of disequilibrium produce different patterns of microlite orientation. We identified two types of reaction rim: Type 1- reaction rim microlites are generally oriented at random and share little or no systematic relationship with the crystallographic orientation of the host amphibole, and; Type 2- reaction rim microlites exhibit a topotactic relationship with the host amphibole (they share the same crystallographic orientation). Experimentally produced heating reaction rims are without exception Type 2. However the natural reaction rims are evenly distributed between Types 1 and 2. Further experimental data on decompression induced reaction rim formation is needed to investigate if Type 1 reaction rims resemble the breakdown of amphibole due to decompression. If so, reaction rim microlite orientation could provide a clear method for distinguishing between heating and decompression processes in amphibole bearing magmas.
De Angelis, Sarah; Lavallķe, Yan; Larsen, Jessica; Mariani, Elisabetta
Characterization by EBSD of dislocations and disclinations in olivine: implications for the rheology of olivine-rich aggregates
NASA Astrophysics Data System (ADS)
The rheology of olivine-rich rocks remains poorly understood. Only intracrystalline deformation mechanisms involving dislocations are quite well known. In orthorhombic olivine only two slip directions, [100] and [001] can be activated. Most characterizations performed so far involve transmission electron microscopy studies at high magnifications or, at a larger scale, optical or scanning electron microscopy on decorated samples. In the latter case, no detailed characterization of the defects could be done. Orientation maps obtained from high-resolution electron backscattered diffraction allow recovering components of the lattice curvature tensor which in turn allow determination of components of the dislocation density tensor. The geometrically necessary dislocation content can thus be imaged. Recently Beausir & Fressengeas (2013) have shown that with this technique, components of the disclination density tensor could also be determined. Several examples have been provided in metallic alloys. In this study we show that olivine aggregates (both experimentally and naturally deformed) contain pervasive evidence of disclinations dipoles at grain boundaries. The implications on the plastic behavior of olivine rocks are discussed based on a numerical model of the response to an applied shear stress of a grain boundary made of disclinations. Beausir, B. & Fressengeas, C., Disclination densities from EBSD orientation mapping. International Journal of Solids and Structures 50 (1), 137-146 (2013).
Cordier, P.; Demouchy, S. A.; Beausir, B.; Taupin, V.; Fressengeas, C.
A methodology to study crystal plasticity inside a compression test sample based on image correlation and EBSD
Modified compression tests in a coarse-grained austenitic stainless steel have been carried out in order to examine the crystal plasticity behavior for large plastic deformations. The measurements of local in-plane strains provide deeper insight into the deformation process on the local scale. These measurements are performed by digital image correlation technique (DIC) in combination with local crystal orientation measurements by using the electron backscatter diffraction technique (EBSD). Split test samples are prepared to track the strong microstructural changes during deformation, which is done incrementally in 10% steps up to 60% total macroscopic strain. The clear correlation of local strains with crystal orientation changes - e.g. in the case of mechanical twinning - permits to identify the acting deformation mechanisms. Such, experimentally determined local strain maps can be used for verification of crystal plasticity finite element method simulations (CPFEM). - Research Highlights: {yields} Method to study large strain crystal plasticity inside an austenitic FeCrNi-alloy. {yields} Correlation of local strain analyses with crystal orientation measurements. {yields} Deformation mechanism changes locally from dislocation glide to mechanical twinning. {yields} Suitable to study grain-grain interactions, slip system activation and grain boundary effects. {yields} Provide essential data for crystal plasticity FEM studies.
Rehrl, C., E-mail: firstname.lastname@example.com [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstr. 12, 8700 Leoben (Austria); Kleber, S. [Boehler Edelstahl GmbH, Kapfenberg, Mariazeller Str. 25, 8605 Kapfenberg (Austria); Antretter, T. [Institute for Mechanics, Montanuniversitaet Leoben, Leoben (Austria); Pippan, R. [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstr. 12, 8700 Leoben (Austria)
Influence of Surface Preparation on Scanning Kelvin Probe Microscopy and Electron Backscatter Diffraction Analysis of Cross Sections of CdTe/CdS Solar Cells: Preprint
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.
The Influence of Sn Orientation on Intermetallic Compound Evolution in Idealized Sn-Ag-Cu 305 Interconnects: an Electron Backscatter Diffraction Study of Electromigration
NASA Astrophysics Data System (ADS)
Previous research showed the relationship between Sn grain orientation and the intermetallic growth rate in Sn-Ag-Cu (SAC)305 interconnects. Samples with the Sn c-axis aligned parallel to the current flow have an intermetallic compound growth rate significantly faster than samples with the c-axis perpendicular to the current flow. This study continues the previous research by investigating intermetallic growth in polygranular joints and in joints that have a thin Ni layer at the cathodic or anodic interface of the interconnect. Planar SAC305 interconnects were sandwiched between two Cu pads (sometimes incorporating a thin Ni layer at the interface) and subjected to uniaxial current. The crystallographic orientation of Sn in these samples was characterized with electron backscatter diffraction before and after electromigration testing. The results show that polycrystalline joints have relatively slow intermetallic growth rates, close to those found in single-crystal joints with the c-axis perpendicular to the current. When a Ni layer was present on the anode side, the intermetallic grew at a rate comparable to that in samples without a Ni layer. However, when the Ni layer was on the cathode side, the intermetallic growth was significantly retarded. The measured growth rates of the intermetallic, combined with literature values for the diffusion of Cu in Sn, were used to calculate values for the effective charge, z *, which is significantly smaller for samples with current parallel to the c-axis than for either polycrystalline samples or samples with the c-axis perpendicular to the electron flow.
Linares, Xioranny; Kinney, Chris; Lee, Kyu-Oh; Morris, J. W.
Use of EBSD to study electropulsing induced reverse phase transformations in a Zn-Al alloy (ZA22).
Multi-phase identification and phase transformations in electropulsing treated Zn-Al based alloy wire specimens were studied using electron back-scattered diffraction, back-scattered scanning electron microscopy and X-ray diffraction techniques. By using electron back-scattered diffraction, two phases: ?'(S) and ?'(T) with a small difference of about 1% in lattice parameters (c(0)/a(0) ) were identified, based on the determined lattice parameters of the phases, and the reverse eutectoid phase transformations: ?'(T) +?'(T) +?'(T) ??'(S) and ?+??T'+? were successfully detected. Electron back-scattered diffraction appeared to be an effective technique for studying complex electropulsing induced phase transformations. PMID:21118233
Zhu, Y H; To, S; Liu, X M
EBSD characterization of high-temperature phase transformations in an Al-Si coating on Cr-Mo steel
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: firstname.lastname@example.com; Wang, Chaur-Jeng
From tabular to rhombohedral dolomite crystals in Zechstein 2 dolostones from Scharzfeld (SW Harz/Germany): A case study with combined CL and EBSD investigations
NASA Astrophysics Data System (ADS)
Tabular dolomite crystals found within dolomite rhombs have been investigated by cathodoluminescence (CL) microscopy and spectroscopy combined with electron backscatter diffraction (EBSD) for the first time. The dolomites formed in the Upper Permian Stassfurt Carbonate Ca2 at the southern margin of the German/Polish Zechstein Basin. Cathodoluminescence petrography of the dolostone succession revealed that the dolomites developed in four phases. Electron backscatter diffraction analysis reveals tabular crystal growth during the two first generations, while the last two generations are characterized by rhombohedral crystal shapes. The tabular dolomite cement crystals and their microcrystalline equivalents in matrix and components have a stoichiometric composition with good to very good lattice ordering. Manganese and iron contents of the tabular crystals are low and their carbon and oxygen isotope composition confirms an early diagenetic dolomite formation under marine-evaporitic conditions from precursor carbonates of Upper Permian age. CL spectroscopy reveals that the tabular dolomite generation 1 has a very high percentage of Mn 2+ on the Ca lattice position which results in a visually yellowish-green CL emission. Although relatively increased Mn 2+ contents at the Ca lattice position appear to be rather common in evaporitic dolomites the combination of a tabular crystal shape and a preferred input of Mn 2+ at the Ca lattice position is a remarkable phenomenon. As tabular dolomite crystals so far are exclusively reported from evaporitic diagenetic settings they could be the result of a high Mg/Ca ratio which blocks c-axis orientated growth of dolomite crystal. The occurrence of well ordered dolomite of which the geochemical zoning can be studied in such detail is rare for the earliest, synsedimentary stages of dolomite formation in marine environments, because these early stages commonly consist of not or badly ordered Ca-dolomites. A primary geochemical zoning of such dolomite usually gets lost during stabilisation and transformation to better ordering and stoichiometry.
Gillhaus, Axel; Richter, Detlev K.; G÷tte, Thomas; Neuser, Rolf D.
Hyperspectral Imaging at the Micro- and Nanoscale using Energy-dispersive Spectroscopy (EDS) with Silicon Drift Detector (SDD) and EBSD Analysis
NASA Astrophysics Data System (ADS)
SDD systems have become state of the art technology in the field of EDS. The main characteristic of the SDDs is their extremely high pulse load capacity of up to 750,000 counts per second at good energy resolution (<123 eV Mn-K?, <46 eV C-K? at 100,000 counts per seconds). These properties in conjunction with electron backscatter diffraction (EBSD) technique and modern data processing allows not only high speed mapping but also hyperspectral analysis. Here, a database is created that contains an EDS spectrum and/or EBSD pattern for each pixel of the SEM image setting the stage for innovative analysis options: The Maximum Pixel Spectrum function [1] synthesizes a spectrum out of the EDS database, consisting of the highest count level found in each spectrum channel. Here, (trace) elements which occur in only one pixel can be detected qualitatively. Areas of similar EDS composition can be made visible with Autophase, a spectroscopic phase detection system. In cases where the crystallographic phase assessment by EBSD is problematic due to pattern similarity, the EDS signal can be used as additional information for phase separation. This paper presents geoscience applications with the QUANTAX system with EDS SDD and EBSD detector using the options described above: (1) Drill core analysis of a Chicxulub impact ejecta sequence from the K/Pg boundary at ODP leg 207 [2] using fast, high resolution element maps. (2) Detection of monazite in granite by the Maximum Pixel Spectrum function. (3) Distribution of elements with overlapping peaks by deconvolution at the example of rare earth elements in zoned monazite. (4) Spectroscopic phase analysis of a sulfate-carbonate-dominated impact matrix at borehole UNAM-7 from the Chicxulub impact crater [3]. (5) EBSD studies with examples of iron meteorites and impact-induced, recrystallized carbonate melts [4]. In addition, continuing technological advances require the elemental analysis of increasingly smaller structures in many fields, including geosciences. It will be demonstrated that using low accelerating voltages, the element distribution of structures at the nanoscale in bulk samples can be displayed in a short time due to optimized signal processing and solid angle. Peaks composed of contributions from several overlapping elements e.g. N-K (392 eV) and Ti-Ll (395 eV) can be deconvolved [6] using an improved atomic database with 250 additional L, M and N lines below 4 keV. Improved light element quantification allows the standardless quantification of features at the nanoscale such as rutile grains 200-500 nm in size. References: [1] Bright D S. & Newbury D. E. (2004) Journal of Microscopy 216:186-193. [2] Schulte P. et al. (2010) Science 327: 1214-1218. [3] Salge T. (2007) PhD thesis: 130p. http://edoc.huberlin.de/docviews/abstract.php?lang=ger&id=27753. [4] Deutsch A. et al. MAPS 45: A45. [6] Tunckan O. (2010) Joining ceramics using capacitor discharge technique and determination of metal ceramic interface reactions, PhD thesis, Anadolu University, Eskisehir, Turkey. Acknowledgements: We thank P. Schulte, A. Deutsch, ODP, L. Hecht, A. Kearsley, J. Urrutria-Fucugauchi, O. Tunckan and S. Turan for generously providing the samples.
Salge, T.; Goran, D.
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.
Seismic properties of the upper mantle beneath Lanzarote (Canary Islands): Model predictions based on texture measurements by EBSD
NASA Astrophysics Data System (ADS)
We present a petrophysical analysis of upper mantle xenoliths, collected in the Quaternary alkali basalt fields (Series III and IV) from the island of Lanzarote. The samples consist of eight harzburgite and four dunite nodules, 5 to 15 cm in size, and exhibit a typical protogranular to porphyroclastic texture. An anomalous foliation resulting from strong recovery processes is observed in half of the specimens. The lattice preferred orientations (LPO) of olivine, orthopyroxene and clinopyroxene were measured using electron backscatter diffraction (EBSD). In most samples, olivine exhibits LPOs intermediate between the typical single crystal texture and the [100] fiber texture. Occasionally, the [010] fiber texture was also observed. Simultaneous occurrence of both types of fiber textures suggests the existence of more than one deformation regime, probably dominated by a simple shear component under low strain rate and moderate to high temperature. Orthopyroxene and clinopyroxene display a weaker but significant texture. The LPO data were used to calculate the seismic properties of the xenoliths at PT conditions obtained from geothermobarometry, and were compared to field geophysical data reported from the literature. The velocity of P-waves (7.9 km/s) obtained for a direction corresponding to the existing seismic transect is in good agreement with the most recent geophysical interpretation. Our results are consistent with a roughly W-E oriented fastest P-wave propagation direction in the uppermost mantle beneath the Canary Islands, and with the lithosphere structure proposed by previous authors involving a crust-mantle boundary at around 18 km in depth, overlaid by intermediate material between 11 and 18 km.
Vonlanthen, Pierre; Kunze, Karsten; Burlini, Luigi; Grobety, Bernard
Acquisition Parameters Optimization of a Transmission Electron Forward Scatter Diffraction System in a Cold-Field Emission Scanning Electron Microscope for Nanomaterials Characterization.
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. SCANNING 9999:XX-XX, 2013. ® 2013 Wiley Periodicals, Inc. PMID:23440636
Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald
Competitive effects of metal dissolution and passivation modulated by surface structure: An AFM and EBSD study of the corrosion of alloy 22
NASA Astrophysics Data System (ADS)
Electron backscatter diffraction (EBSD) and atomic force microscopy (AFM) are used to correlate crystallographic grain orientation with corrosion rates of polycrystalline alloy 22 following immersion in 1 and 3 molar (M) hydrochloric acid. For each acid concentration, relative corrosion rates are simultaneously characterized for approximately 50 unique grain orientations. The results demonstrate that the corrosion rate anisotropies are markedly different in the two acid concentrations. In very aggressive acidic environments (3M HCl), where electrochemical impedance spectroscopy and spectroscopic ellipsometry data demonstrate that the passive oxide film of alloy 22 is completely dissolved, alloy dissolution rates scale inversely with the average coordination number of surface atoms for a given grain orientation, where highly correlated surfaces dissolve the slowest. Thus, similar to simple metallic systems, the corrosion rates scale with the surface plane-normal crystallographic orientations as {1 1 1} < {1 0 0} < {1 1 0}. Less intuitively, in milder corrosive environments (1M HCl), where the passive film of the alloy is still intact, the dissolution does not scale inversely with surface atomic density. Rather, corrosion rates scale with crystallographic orientations as {1 1 1} < {1 1 0} < {1 0 0}. This is attributed to the fact that facets most susceptible to corrosion (least coordinated) are also the most able to form protective oxides, so that the dissolution anisotropy is a result of the delicate balance between metal dissolution and oxide growth.
Gray, J. J.; El Dasher, B. S.; Orme, C. A.
Influence of the Pt barrier on Ti\\/Al\\/Pt\\/Au ohmic contacts to n-GaN studied by Rutherford backscattering spectrometry and x-ray diffraction
The diffusion barrier effect of Pt has been investigated in Ti\\/Al\\/Pt\\/Au ohmic contacts to n-GaN. Severe indiffusion, outdiffusion of Pt and outdiffusion of Ga have been found in 450 ░C annealed samples according to the Rutherford backscattering spectrometry (RBS) results. At the same time, the reaction between Ga and Pt has also been identified by glancing angle synchrotron irradiation x-ray
C. Y. Hu; Z. B. Ding; Z. X. Qin; Z. Z. Chen; Y. J. Wang; Z. J. Yang; X. D. Hu; T. J. Yu; L. S. Yu; S. D. Yao; G. Y. Zhang
Electromagnetic backscattering by plates and disks
NASA Technical Reports Server (NTRS)
With the recent development of diffraction coefficients for imperfectly conducting half-planes, it has become possible to analyze a wide variety of problems for which the impedance surface boundary condition applies. This impedance boundary condition, while approximate, was utilized to extend the usefulness of the Uniform Geometrical Theory of Diffraction (UTD) beyond the perfectly conducting geometries. These half-plane diffraction coefficients are used to analyze patterns of an antenna in the presence of an imperfectly conducting flat polygonal plate. The Geometrical Theory of Diffraction (GTD) techniques were also used to investigate the backscattering from perfectly conducting plates. 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 was obtained and used to find an additional component of the backscattered field. The backscattering from a square plate was then analyzed using GTD. Backscattering in both the principal and off-principal planes was examined.
Balanis, Constantine A.; Griesser, Timothy; Marsland, Diane M.
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.
EBSD and TEM Characterization of High Burn-up Mixed Oxide Fuel
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; Brian P. Gorman; Brandon D Miller; Jeffrey King
Annealing twin formation and recrystallization study of cold-drawn copper wires from EBSD measurements
The crystallographic texture and microstructure of an electrolytic tough pitch copper have been investigated by Electron Back Scattered Diffraction (EBSD) after cold wire drawing (reduction in area between 52% and 94%) and after primary recrystallization. The material presents a deformation texture composed of major <111> and minor <100> fibers. The evolution of the quality index of the Kikuchi patterns shows that the stored energy is lower in the <100> fiber than in the <111> fiber. Then, after recrystallization, the volume fraction of the <100> fiber increases at the expense of the other texture components. The study of the grain boundary nature shows that the recrystallization twin fraction decreases with increasing strain. It is shown that this evolution is the consequence of the grain size reduction.
Baudin, T. [Universite de Paris Sud, ICMMO, UMR CNRS 8182, Laboratoire de Physico-Chimie de l'Etat Solide, batiment 410, 91405 Orsay Cedex (France)], E-mail: email@example.com; Etter, A.L.; Penelle, R. [Universite de Paris Sud, ICMMO, UMR CNRS 8182, Laboratoire de Physico-Chimie de l'Etat Solide, batiment 410, 91405 Orsay Cedex (France)
A simulation of recrystallization based on EBSD orientation microscopy data
The present paper introduces a novel stochastic two-dimensional model to simulate the evolution of microstructure and texture during recrystallization. The model is based on data derived by automated large-scale EBSD local texture analysis, i.e., by orientation microscopy. Each measured point is characterized by its coordinates x and y in the microstructure, its crystallographic orientation g and a parameter q describing the quality of the EBSD-pattern which is affected by lattice strain and hence discloses information on the dislocation density. The concurrent information on the local arrangement of orientations and dislocation densities is utilized to derive conclusions on the nucleation and subsequent growth of the new recrystallized grains. The principles of the model are outlined and three example are shown to illustrate the possibilities of the model to simulate the evolution of microstructure and texture during recrystallization.
Engler, O.
Rutherford Backscattering Spectrometry.
National Technical Information Service (NTIS)
The bases of Rutherford ion backscattering and its combination with channeling effect technique are reviewed. This combined method is referred to as backscattering spectrometry. The measurement of chemical compositions, the detection of crystal defects, e...
J. Gyulai
Rutherford Backscattering Spectrometry.
National Technical Information Service (NTIS)
The bases of Rutherford ion backscattering and its combination with channeling effect technique are reviewed. This combined method is recently referred to as Backscattering Spectrometry. The measurement of chemical compositions, the detection of crystal d...
J. Gyulai
SEM, EDS, EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys
The microstructure of centrifugally cast heat resistant alloys of the HP-series (Fe-35Ni-25Cr-0.4C, wt.%) contains several minor phases, like carbides (M{sub 7}C{sub 3}, M{sub 23}C{sub 6} and MC). Several alloys are characterized by means of scanning electron microscopy in back-scattered electron imaging and energy dispersive spectroscopy, of electron probe micro-analysis by X-ray wavelength dispersive spectroscopy, and of electron back-scattered diffraction. On the one hand, scanning electron microscopy imaging in the back-scattered mode, associated with energy dispersive spectroscopy analysis and electron back-scattered diffraction, can lead to the identification of all phases, but with a lack of accuracy in certain cases. On the other hand, electron probe micro-analysis by X-ray wavelength dispersive spectroscopy alone can always provide a strict identification of all phases, with additional precise information on phase composition, including for light elements, which is important in the case of carbides.
Laigo, J. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Air Liquide, Centre de Recherche Claude-Delorme, 1, chemin de la Porte des Loges, 78354 Jouy-en-Josas (France); Christien, F.; Le Gall, R. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Tancret, F. [Universite de Nantes, Nantes Atlantique Universites, Polytech'Nantes, LGMPA, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France)], E-mail: firstname.lastname@example.com; Furtado, J. [Air Liquide, Centre de Recherche Claude-Delorme, 1, chemin de la Porte des Loges, 78354 Jouy-en-Josas (France)
Thermal Neutron Backscatter Imaging.
National Technical Information Service (NTIS)
Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form ...
P. Vanier
Synchrotron X-Ray Diffraction Study of Texture Evolution in 904L Stainless Steel under Dynamic Shock Compression
NASA Astrophysics Data System (ADS)
The influence of strain rate on development of deformation texture under a dynamic shock compression of a 904L stainless steel was quantitatively investigated using synchrotron X-ray diffraction and crystallographic orientation distribution function (ODF) analysis. The Split-Hopkinson Pressure Bar (SHPB) technique was used to generate a high strain rate of >103 s-1 for preparing the deformed samples. Starting with an almost random texture in a solution treatment condition, the deformed material developed several typical texture components, such as Goss texture and Brass texture. Compared to the texture components displayed in the state of quasi-static compression deformation, it was found that the high-speed deformation generated much weaker texture components. In combination with the change in microstructures observed by electron backscattering diffraction (EBSD) and the transmission electron microscopy (TEM) technique, the high-energy X-ray diffraction provides a powerful tool for characterizing the strain-rate dependence of grain rotation at each stage of deformation. The deformation heterogeneity evident in our experiment can be explained by a transition of deformation mechanism from the dislocation/twin-dominated mode to a shear-band-dominated one with increasing strain rate.
Li, N.; Wang, Y. D.; Lin Peng, R.; Sun, X.; Ren, Y.; Wang, L.; Cai, H. N.
Diffraction-based study of fatigue crack initiation and propagation in aerospace aluminum alloys
NASA Astrophysics Data System (ADS)
The crack initiation sites and microstructure-sensitive growth of small fatigue cracks are experimentally characterized in two precipitation-hardened aluminum alloys, 7075-T651 and 7050-T7451, stressed in ambient temperature moist-air (warm-humid) and -50░C dry N2 (cold-dry) environmental conditions. Backscattered electron imaging (BSE) and energy dispersive spectroscopy (EDS) of the fracture surfaces showed that Fe-Cu rich constituent particle clusters are the most common initiation sites within both alloys stressed in either environment. The crack growth within each alloy, on average, was observed to be slowed in the cold-dry environment than in the warm-humid environment, but only at longer crack lengths. Although no overwhelming effects of grain boundaries and grain orientations on small-crack growth were observed, crack growth data showed local fluctuations within individual grains. These observations are understood as crack propagation through the underlying substructure at the crack surface and frequent interaction with low/high-angle grain and subgrain boundaries, during cyclic loading, and, are further attributed to periodic changes in crack propagation path and multiple occurrences of crack-branching observed in the current study. SEM-based stereology in combination with electron backscattered diffraction (EBSD) established fatigue crack surface crystallography within the region from ś1 to 50 mum of crack initiating particle clusters. Fatigue crack facets were parallel to a wide variety of crystallographic planes, with pole orientations distributed broadly across the irreducible stereographic triangle between the {001} and {101}-poles within both warm-humid and cold-dry environments. The results indicate environmentally affected fatigue cracking in both cases, given the similarity between the observed morphology and crystallography with that of a variety of aerospace aluminum alloys cracked in the presence of moist-air. There was no evidence of crystallographic {111} slip-plane cracking typical of the Stage I crack growth mode observed in single crystals and high purity polycrystals of face centered cubic metals, and which has presently been assumed for the present materials within fatigue crack initiation models. Rather, the facets tend to have near-Mode I spatial orientation, which is another indicator of the importance of environmentally affected fatigue damage. The results provide a physical basis to develop microstructurally-based next generation multi-stage fatigue (MSF) models that should include a new crack decohesion criteria based upon environmental fatigue cracking mechanisms. EBSD study of small-cracks in alloy 7050-T7451, stressed in warm-humid environment, showed that crack-path orientation changes and crack-branching occurred at both low/high-angle grain and subgrain boundaries. Single surface trace analysis suggests that the crack-path differs substantially from crystallographic slip-planes. EBSD-based observations of small-crack propagation through subgrain structure, either formed by cyclic plastic strain accumulation or pre-existing (typical of unrecrystallized grain structure in the present materials), suggest that subgrain structure plays a crucial role in small fatigue crack propagation. As mentioned earlier, local fluctuations in small-crack growth rates appear to be caused by frequent interaction with subgrain boundaries, and multiple occurrences of crack-branching and crack-path orientation changes at low/high-angle grain and subgrain boundaries. The aforementioned deviation from low-index {001}/{101}-planes and the occurrence of high-index cracking planes observed by EBSD/Stereology, in this study and others, are interpreted as trans-subgranular decohesion or inter-subgranular cracking, due to trapped hydrogen. In summary, the results provide a firmer experimental foundation for, and clearer understanding of, the mechanisms of environmental fatigue cracking of aluminum alloys, especially the role of inter-subgranular cracking, which had previously been advanced based upon fracture su
Gupta, Vipul K.
NASA Technical Reports Server (NTRS)
In the past year, NOAA has measured and analyzed another year's worth of backscatter over Boulder, CO. The average profile was computed from 80 satellite observations of backscatter spread throughout the year, using NOAA's CO2 coherent lidar operating at a wavelength of 10.59 microns. The seasonal averages show a familiar trend (highest backscattering in spring, perhaps due to Asian dust or biomass burning, and lowest backscattering in fall). The 1990 average profile was not significantly different from the 1988 or 1989 profiles, except that it displays a slight increase in the upper troposphere, perhaps due to the Redoubt Volcano. The NOAA's backscatter processing program (BETA) was refined to enable the calculation of gaseous absorption effects based on rawinsonde measurements, as well as using atmospheric models. NOAA participated in two intercomparisons of aerosol measuring instruments near Boulder, called FRLAB (Front Range Lidar, Aircraft, and Balloon Experiment). Considerable effort was also put into developing a multiagency science proposal to NASA headquarters to work with both JPL and NASA-Marshall to produce an airborne Doppler lidar facility for the DC-8.
Post, Madison J.
Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.
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
Future prospects on EBSD speeds using a 40 nA FESEM
This paper describes a method of estimating the maximum obtainable mapping speed by the use of a new ultra-fast EBSD detector\\u000a system [1], both with current equipment and with even faster CCDs that will be available in the future.
M. S°fferud; J. Hjelen; M. Karlsen; D. Dingley; H. Jaksch
EBSD study on the formation of fine ferrite grains in plain carbon steel during warm deformation
Torsion testing was carried out on a plain carbon steel to study ferrite grain refinement during warm deformation within two-phase (?+?) region. Fine ferrite grains development was analyzed by using optical microscope and EBSD technique. Microstructural analysis shows that with increasing strain the new fine equiaxed ferrite grains surrounded by high angle boundaries start generating at the initial boundaries and
B. Eghbali
Backscatter digital holography of microparticles.
This work investigates a method for digital holographic imaging of microparticles. Traditional digital holographic techniques use a particle's forward scattered light to form the hologram, whereas here we use the backscattered light. Images of a particle are then computationally reconstructed from the backscatter hologram, and several examples of such reconstructions are presented. A potential advantage of this technique is that the backscatter holograms may be more sensitive to particle-surface details. PMID:23736480
Subedi, Nava R; Fowler, Nicholas B; Berg, Matthew J
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.
Backscattering reciprocity for large particles.
The backscattering reciprocity theorem is considered for large particles as compared with the incident wavelength particles of arbitrary shape. It is shown that, in the specific case of faceted particles, this theorem is provided by the appearance of pairs of conjugate backscattered beams. A parameter characterizing a deviation of any approximation from the reciprocity theorem is proposed, and it is used for estimation of reliability for the physical-optics approximation. PMID:23632526
Borovoi, Anatoli; Konoshonkin, Alexander; Kustova, Natalia
EBSD coupled to SEM in situ annealing for assessing recrystallization and grain growth mechanisms in pure tantalum.
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; Logķ, R E; Jacomet, S; Llorca, V; Bozzolo, N
Effect of the cortex on ultrasonic backscatter measurements of cancellous bone
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 ōapparentö 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.
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.
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 100Ąm 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, HÕkon; Putnis, Andrew
NASA Astrophysics Data System (ADS)
In contrast to transmission X-ray imaging systems where inspected objects must pass between source and detector, Compton backscatter imaging allows both the illuminating source as well as the X-ray detector to be on the same side of the target object, enabling the inspection to occur rapidly and in a wide variety of space-constrained situations. A Compton backscatter image is similar to a photograph of the contents of a closed container, taken through the container walls, and highlights low atomic number materials such as explosives, drugs, and alcohol, which appear as especially bright objects by virtue of their scattering characteristics. Techniques for producing X-ray images based on Compton scattering will be discussed, along with examples of how these systems are used for both novel security applications and for the detection of contraband materials at ports and borders. Differences between transmission and backscatter images will also be highlighted. In addition, tradeoffs between Compton backscatter image quality and scan speed, effective penetration, and X-ray source specifications will be discussed.
Dinca, Dan-Cristian; Schubert, Jeffrey R.; Callerame, J.
Softening of hard bremsstrahlung by Compton backscattering
Multimegavolt bremsstrahlung backscattering from paraffin yields a photon spectrum mainly below 0.6 MeV. The measured dose in the backscattered radiation agrees with Monte Carlo computations to within 10%.
Whittaker, D.A.; Kerris, K.G.; Litz, M.; Gorbics, S.G.; Pereira, N.R.
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
Backscatter measurements for NIF ignition targets (invited)
Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near backscatter imager (NBI) instrument separately measure the stimulated Brillouin and stimulated Raman scattered light. Both instruments work in conjunction to determine the total backscattered power to an accuracy of {approx}15%. In order to achieve the power accuracy we have added time-resolution to the NBI for the first time. This capability provides a temporally resolved spatial image of the backscatter which can be viewed as a movie.
Moody, J. D.; Datte, P.; Krauter, K.; Bond, E.; Michel, P. A.; Glenzer, S. H.; Divol, L.; Suter, L.; Meezan, N.; MacGowan, B. J.; Hibbard, R.; London, R.; Kilkenny, J.; Wallace, R.; Knittel, K.; Frieders, G.; Golick, B.; Ross, G.; Widmann, K.; Jackson, J. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550 (United States); and others
Backscatter absorption gas imaging system
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)
Optical backscatter of marine flocs
NASA Astrophysics Data System (ADS)
Marine flocs (defined here as aggregated particles >10 ?m diameter) derived from phytoplankton culture ( Phaeodactylum tricornutum; PT) and water-based drilling mud (WBDM) waste were generated in an enclosed upwelling system in order to examine how optical backscatter coefficients at six wavelengths changed as flocs matured. Equilibrium was reached after death of the phytoplankton cells and was identified as a consistent particle projected-area concentration of flocs (>10 ?m diameter) despite compensating changes in the number and average size of flocs. As the suspension of flocs matured, the particle backscatter coefficients at six optical wavelengths increased as a function of increasing particle projected-area concentration, despite a drop in the mass of suspended particulate matter (SPM). In this flocculating suspension, the mass of suspended particles and the particle projected-area concentration were not co-variates. These results indicate that the strong response of optical backscatter (OBS) to particle size in many previous studies may simply be due to the inappropriate use of weight concentration as the independent variable, rather than particle projected-area concentration.
Hatcher, Annamarie; Hill, Paul; Grant, Jon
Formation of Equiaxed Alpha and Titanium Nitride Precipitates in Spark Plasma Sintered TiB/Ti-6Al-4V Composites (Preprint).
National Technical Information Service (NTIS)
Spark plasma sintered TiB/Ti-6Al-4V composites have been characterized using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). As-SPS processed composites exhibit a more refined distr...
J. Y. Hwang M. Y. Koo P. Nandwana R. Banerjee S. H. Hong
Three-Dimensional Crystal Structure Mapping by Diffractive Scanning Confocal Electron Microscopy (SCEM)
NASA Astrophysics Data System (ADS)
Recently a diffracted-probe scanning confocal electron microscopy (SCEM) mode was demonstrated. Analysis of such diffracted-probe images yields the sample height (defocus), thickness and crystal orientation. An extension of this principle for three-dimensional (3D) mapping is described and preliminary bicrystal data presented. Additional experimental criteria are discussed and the 3D resolution of this new diffractive SCEM mapping is derived and was found to be ?20 nm and is comparable with 3D FIB-EBSD in terms of both field-of-view, spatial resolution and acquisition time.
Jones, Lewys; Wang, Peng; Nellist, Peter D.
Backscattering X-ray standing waves in the XUV region.
It is demonstrated that Bragg reflection of XUV radiation can be used to study structural properties of crystalline materials with large unit cells. A standing-wave field is formed in a layered TiSe2 single crystal for a near-backscattering geometry (theta = 88.5 degrees). The partial electron yield is measured as a function of photon energy across the (001) Bragg reflection condition (hv approximately equal to 1033 eV) and its characteristic modulation is compared with the results derived from dynamical diffraction theory in the two-wave approximation. The data reveal a large amount of disorder along the c-axis. PMID:11486406
Grehk, T M; Drube, W; Kipp, L; Materlik, G
The coherent backscattering opposition effect
NASA Technical Reports Server (NTRS)
We have measured the opposition effect, the nonlinear surge in reflectance seen in particulate materials as phase angle approaches zero degrees, in a suite of materials of varying particle size and reflectance. These samples were illuminated by linearly and circularly polarized monochromatic radiation at two wavelengths, 0.442 and 0.633 microns. By measuring the linear and circular polarization ratios for each sample, we have found that in highly reflective materials the behavior of the reflected radiation is consistent with the coherent backscattering process which has recently been proposed to explain the opposition surge that is seen in such media. The size and width of the coherent backscattering opposition peak vary as a function of reflectance of the sample. The opposition effect has been observed in particulate materials studied in the laboratory and it is also observed in the radiation reflected from solar system bodies which present a regolith to the earth based observer. The traditional explanation of the opposition effect, the shadow-hiding hypothesis, is that it was caused by the elimination of mutual shadows cast between the regolith grains as the phase angle of the observation became smaller. This shadow-hiding hypothesis, however, is unable to explain the opposition effect seen in highly reflective materials such as magnesium oxide and barium sulfate powders. This is because highly reflective media will multiply scatter the incident radiation between the regolith grains. This causes the shadows to be eliminated. We have measured the angular scattering properties of a suite of materials of different reflectivity. We have observed polarization ratios in reflective particulates that are consistent with coherent backscattering as the principal process which causes the opposition surge.
Nelson, R. M.; Hapke, B. W.; Smythe, W. D.; Gharakanian, V.; Herrera, P.
Polarimetric backscattering from sea ice
NASA Technical Reports Server (NTRS)
Polarimetric backscattering from sea ice is presented. Theoretical models for backscattering are first presented for various ice types. Then, theoretical results are compared with experimental data for new thin ice, first-year ice, and multi-year ice. Sea ice is modeled as a layer medium containing random scatterers and rough interfaces. For multi-year sea ice with snow cover, the sea ice layer is modeled as an ice background with embedded spheroidal air bubbles and the snow layer as air with ice grains. The hummocky topography on multi-year ice is characterized by a Gaussian distribution which has an averaging effect on backscattering coefficients. First-year sea ice is described by an ice medium hosting ellipsoidal brine inclusions. These inclusions are oriented preferentially in the vertical direction due to the columnar structure of first-year sea ice. Azimuthally, the orientation of the brine pockets are random corresponding to the random c-axes in sea ice, unless the axes are oriented by sea currents. For thin ice in newly opened leads, it has been observed that there exists a thin brine layer with very high salinity on the top surface of the new ice. This brine layer is depicted as a medium with high permittivity which can significantly affect electromagnetic scattering signatures from the lower thin ice layer, with a higher fractional volume of brine inclusions due to higher salinity as compared to thick first-year sea ice. The rough medium interfaces are described as Gaussian rough surfaces characterized by root-mean-square heights and surface correlation lengths. The contribution from rough surface, calculated under the Kirchhoff approximation or small perturbation method, is assumed to be independent from volume scattering. The total loss including absorption and scattering losses in the scattering media is represented by the imaginary part of effective permittivity obtained from the strong fluctuation theory. The polarimetric scattering coefficients for different ice types are then derived under the distorted Born approximation.
Nghiem, S. V.; Kwok, R.; Yueh, S. H.
Processing, properties, and application of textured 0.72lead(magnesium niobate)-0.28lead titanate ceramics
In this study, XRD and electron backscatter diffraction (EBSD) techniques were used to characterize the fiber texture in oriented PMN-28PT and the intensity data were fit with a texture model (the March-Dollase equation) that describes the texture in terms of texture fraction (f), and the width of the orientation distribution (r). EBSD analysis confirmed the orientation of the microstructure, with
Kristen H. Brosnan
A study of the surface deformation behaviour at grain boundaries in an ultra-low-carbon steel
Tensile specimens of ultra-low-carbon ferritic steel with two different grain sizes were studied by atomic force microscopy (AFM) and electron backscatter diffraction (EBSD) after different plastic strains up to 10%. Different parameters, such as the change in surface roughness and the change in misorientation with strain, were evaluated. There was good agreement between the AFM and EBSD results. Both the
Dilip Chandrasekaran; Mikael NygÕrds
X-ray microdiffraction and EBSD study of FSP induced structural\\/phase transitions in a Ni-based superalloy
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
Oleg M. Barabash; Rozaliya I. Barabash; Gene E. Ice; Zhili Feng; David Gandy
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.
Millimeter wave backscatter from deciduous trees
Measurements of the millimeter-wave backscatter from deciduous (leafed) trees are explained using a simple scattering model. The backscatter from individual leaves was measured in the laboratory and used to justify the use of an average leaf radar cross section when computing the normalized radar cross section (NRCS) of tree canopies. NRCS measurements of canopies show that the direction in which
Christoph C. Borel; ROBERT E. McINTOSH
Biomedical applications of enhanced backscattering spectroscopy
Enhanced Backscattering Spectroscopy enables minimally invasive measurement of optical properties of biological tissues by characterizing the shape of backscattered light in both angle and spectrum. The peak in scattering intensity in the retroreflection direction depends on the scattering properties of a random medium including mean free path, anisotropy, and even higher order characteristics such as mass fractal dimension. These properties
Jeremy D. Rogers; Nikhil Mutyal; Andrew Radosevich; Vladimir Turzhitsky; Hemant Roy; Vadim Backman
The properties of particle clusters produced in the processes of single and double diffraction dissociation of protons at high energies are reviewed. These clusters appear as jets close to the direction of the dissociating protons and are referred to as diffractive or forward jets. (GHT)
Goulianos, K.
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.
National Technical Information Service (NTIS)
The equations governing the geometrical approximation for nonlinear wave propagation that were derived in a previous paper of this series are used here to construct a special solution that describes diffraction at an edge. The effect described is a purely...
F. E. Bisshopp
Enhanced spontaneous backscattering in Brillouin dynamic gratings.
Spontaneous Brillouin backscattering, which accompanies the operation of Brillouin dynamic gratings (BDGs) setups, is investigated both theoretically and experimentally. It is shown that this noisy emission, which cannot be separated from the signal of interest, contains not only the probe spontaneous Brillouin backscattering but also a significant contribution from the spontaneous/stimulated acoustic field, originating from the high-frequency writing pump. In the absence of the low-frequency writing pump and for a strong enough high-frequency writing pump, the observed Stokes noise can exhibit an average backscattered power much higher than that from the probe alone. PMID:24281529
Yaron, L; Peled, Y; Langer, T; Tur, M
An efficient method for computing backscattering from Born objects of arbitrary shape.
A method is presented for efficiently computing the propagating pressure field backscattered by an arbitrarily shaped, weakly scattering, three-dimensional object. This is accomplished by drawing upon a previously reported relationship between the boundary condition on a two-dimensional radiating aperture and the pressure propagating along an axis normal to the aperture, and the fundamental theorem of diffraction tomography, which relates the Fourier transform of an object function to its scattered pressure field. Together, these two results are used to derive an integral formula that expresses the pressure field backscattered from an object as a one-dimensional Fourier transform of its scattering amplitude. This formula is then utilized to compute the backscattered pressure field from a uniform fluid sphere in the first Born approximation; the results of which are compared to the rigorous partial wave expansion. PMID:21682373
Pees, Edward H
Troubleshoot reboilers by neutron backscatter
At Quantum`s ethylene plant (Morris, ILL.), the capacity of a fractionator was limited by heat transfer in the refrigerated reboilers. Yet, calculations showed that the reboilers should have had ample heat transfer area. To pinpoint the reboiler bottleneck, a task force turned to neutron backscatter. The parallel, vertical thermosyphon reboilers are heated by condensing refrigerant vapor in the shell. Boilup is controlled by varying condensate level in the reboilers--the lower the level, the greater the surface area available for condensation. In general, condensate levels should indicate how much additional heat transfer capacity is available. A low level suggests that little additional boilup is achievable, while a 50% liquid level suggests that the reboiler could produce twice the boilup rate, if no other bottlenecks were encountered. To detect level in a closed vessel, the source probe is moved up and down the vessel surface. Fast neutrons penetrate the vessel walls. As the neutrons interact with the fluid inside, their velocity is slowed by the hydrogen nuclei in the fluid. Slow neutrons diffuse back out from the vessel. The detector counts these slow neutrons, and correlates the count to the concentration of hydrogen atoms inside. Since hydrogen atom concentration is greater in liquid than in vapor, detector response changes sharply at the liquid-vapor interface.
Kister, H.; Pathak, H.; Korst, M.; Strangmeier, D.; Carlson, R.
Examination of Bragg backscattering from crystalline quartz
NASA Astrophysics Data System (ADS)
The backscattering silicon single crystals normally used for hard X-ray inelastic scattering experiments suffer from parasitic reflections and gaps in photon energy where no backscattering reflection exists. Sapphire has been proposed as a possible alternative, but quartz may have advantages over sapphire at low photon energies (5 12.5 keV). Calculations of energy widths of backscattering reflections up to 30 keV for silicon, sapphire, and quartz are compared. The quartz (11 6 0) reflection is examined at 0.03░ from backscattering with 0.8 meV bandwidth beam, and its energy width is measured. Finally, the thermal expansions of quartz and silicon are compared.
Sutter, John P.; Baron, Alfred Q. R.; Ishikawa, Tetsuya; Yamazaki, Hiroshi
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.
Coherent microwave backscatter of natural snowpacks
NASA Technical Reports Server (NTRS)
The backscatter of natural snowpacks was measured using a swept-frequency system operating from 5.8 to 8.0 GHz. Snow layering produced sequences of maxima and minima in backscatter intensity, with typical peak-to-valley ratios of 15 db. Wetness produced in the upper portion of the snowpack by solar heat input enhanced the effect of layering. The layer response persisted for incidence exhibits predominantly coherent properties. Frequency modulation of the incident signal masked the layer response by averaging the unmodulated response over the bandwidth represented by the modulation. Further changes in backscatter were attributed to changes in wetness in the surface regions of the snowpack; for a fixed frequency of 13.5 GHz and incidence angle of 39 deg, the backscatter decreased typically 15 db between 11 A.M. and noon, and returned to approximately its initial level of overnight.
Linlor, W. I.; Angelakos, D. J.; Clapp, F. D.; Smith, J. L.
Low Grazing Angle Tarrain Backscattering Coefficient Generator.
National Technical Information Service (NTIS)
A near-horizon probabilistic terrain backscatter coefficient generator is introduced, combining modified sea-state curves with Weibull-type probability density functions. A total of nine terrain type classifications (soils & rocks, trees, grasses, shrubs,...
W. N. O'Connor
Observation of high-temperature phase transformation in the Si-modified aluminide coating on mild steel using EBSD
Mild 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 deg. C in static air was analyzed by Electron Backscatter Diffraction. The results showed that the aluminide layer of the as-coated specimen consisted of an outer Al-Si eutectic topcoat and the inner Fe-Al-Si and Fe-Al intermetallic layers. The formation of {tau}{sub 5}-Al{sub 7}Fe{sub 2}Si and {tau}{sub 6}-Al{sub 4}FeSi was observed with increasing exposure time at 750 deg. C, while the {tau}{sub 1}-(Al,Si){sub 5}Fe{sub 3} phase precipitated into the Fe{sub 2}Al{sub 5} phase. After 60 min of exposure, the {tau}{sub 5}-Al{sub 7}Fe{sub 2}Si and {tau}{sub 6}-Al{sub 4}FeSi phases disappeared. 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 growing FeAl phase decreased the thickness of Fe{sub 2}Al{sub 5} and forced the formation of FeAl{sub 2} phase. Finally, the aluminide layer comprised only FeAl{sub 2} and FeAl.
Cheng, Wei-Jen, E-mail: email@example.com [Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 10672, Taiwan (China); Wang, Chaur-Jeng [Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei 10672, Taiwan (China)
Lidar backscattering measurements of background stratospheric aerosols
NASA Technical Reports Server (NTRS)
A comparative lidar-dustsonde experiment was conducted in San Angelo, Texas, in May 1974 in order to estimate the uncertainties in stratospheric-aerosol backscatter for the NASA Langley 48-inch lidar system. The lidar calibration and data-analysis procedures are discussed. Results from the Texas experiment indicate random and systematic uncertainties of 35 and 63 percent, respectively, in backscatter from a background stratospheric-aerosol layer at 20 km.
Remsberg, E. E.; Northam, G. B.; Butler, C. F.
Lidar backscattering measurements of background stratospheric aerosols
A comparative lidar-dustsonde experiment was conducted in San Angelo, Texas, in May 1974 in order to estimate the uncertainties in stratospheric-aerosol backscatter for the NASA Langley 48-inch lidar system. The lidar calibration and data-analysis procedures are discussed. Results from the Texas experiment indicate random and systematic uncertainties of 35 and 63 percent, respectively, in backscatter from a background stratospheric-aerosol layer
E. E. Remsberg; G. B. Northam; C. F. Butler
Depolarization of backscattered linearly polarized light
NASA Astrophysics Data System (ADS)
We formulate a quantitative description of backscattered linearly polarized light with an extended photon diffusion formalism taking explicitly into account the scattering anisotropy parameter g of the medium. From diffusing wave spectroscopy measurements, the characteristic depolarization length for linearly polarized light, lp, is deduced. We investigate the dependence of this length on the scattering anisotropy parameter g spanning an extended range from -1 (backscattering) to 1 (forward scattering). Good agreement is found with Monte Carlo simulations of multiply scattered light.
Rojas-Ochoa, Luis Fernando; Lacoste, David; Lenke, Ralf; Schurtenberger, Peter; Scheffold, Frank
Spectral variability of the particulate backscattering ratio
NASA Astrophysics Data System (ADS)
The spectral dependency of the particulate backscattering ratio is relevant in the fields of ocean color inversion, light field modeling, and inferring particle properties from optical measurements. Aside from theoretical predictions for spherical, homogeneous particles, we have very limited knowledge of the actual in situ spectral variability of the particulate backscattering ratio. This work presents results from five research cruises that were conducted over a three-year period. Water column profiles of physical and optical properties were conducted across diverse aquatic environments that offered a wide range of particle populations. The main objective of this research was to examine the behavior of the spectral particulate backscattering ratio in situ, both in terms of its absolute magnitude and its variability across visible wavelengths, using over nine thousand 1-meter binned data points for each of five wavelengths of the spectral particulate backscattering ratio. Our analysis reveals no spectral dependence of the particulate backscattering ratio within our measurement certainty, and a geometric mean value of 0.013 for this dataset. This is lower than the commonly used value of 0.0183 from PetzoldÆs integrated volume scattering data. Within the first optical depth of the water column, the mean particulate backscattering ratio was 0.010.
Whitmire, A. L.; Boss, E.; Cowles, T. J.; Pegau, W. S.
NASA Astrophysics Data System (ADS)
We discuss basic concepts and properties of diffractive phenomena in soft hadron collisions and in deep-inelastic scattering at low Bjorken-x. The paper is not a review of the rapidly developing field but presents an attempt to show in simple terms the close inter-relationship between the dynamics of high-energy hadronic and deep-inelastic diffraction. Using the saturation model of Golec-Biernat and W³sthoff as an example, a simple explanation of geometrical scaling is presented. The relation between the QCD anomalous multiplicity dimension and the Pomeron intercept is discussed.
de Wolf, E. A.
National Technical Information Service (NTIS)
the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquito...
M. Hart
The powder diffraction method, by using conventional X-ray sources, was devised independently in 1916 by Debye and Scherrer in Germany and in 1917 by Hull in the United States. The technique developed steadily and, half a century later, the `traditional' applications, such as phase identification, the determination of accurate unit-cell dimensions and the analysis of structural imperfections, were well established.
J. Ian Langford; Daniel Louļr
Time domain attenuation estimation method from ultrasonic backscattered signals
Ultrasonic attenuation is important not only as a parameter for characterizing tissue but also for compensating other parameters that are used to classify tissues. Several techniques have been explored for estimating ultrasonic attenuation from backscattered signals. In the present study, a technique is developed to estimate the local ultrasonic attenuation coefficient by analyzing the time domain backscattered signal. The proposed method incorporates an objective function that combines the diffraction pattern of the source/receiver with the attenuation slope in an integral equation. The technique was assessed through simulations and validated through experiments with a tissue mimicking phantom and fresh rabbit liver samples. The attenuation values estimated using the proposed technique were compared with the attenuation estimated using insertion loss measurements. For a data block size of 15 pulse lengths axially and 15 beamwidths laterally, the mean attenuation estimates from the tissue mimicking phantoms were within 10% of the estimates using insertion loss measurements. With a data block size of 20 pulse lengths axially and 20 beamwidths laterally, the error in the attenuation values estimated from the liver samples were within 10% of the attenuation values estimated from the insertion loss measurements.
Ghoshal, Goutam; Oelze, Michael L.
Estimating backscatter spectra after deconvolution with Kalman smoothing
NASA Astrophysics Data System (ADS)
In quantitative tissue characterization. Obtaining processed ultrasonic echoes with a direct relationship to local tissue response (backscatter spectrum) and that are free from systemic depth-dependent effects, such as diffraction, is essential. In general practice today, these unwanted distortions are eliminated by dividing short time power spectra. However, this method has its drawbacks; noise is not taken into account, and shorter time gates lead to an increasing bias within the relative spectra. To overcome these methodological issues, I propose a different approach as follows. Entire deconvolved A-scans are estimated by a Kalman smoothing deconvolution algorithm. These then serve as a basis for estimating the relative backscatter spectra. In addition, due to the principle of the deconvolution algorithm, it is possible to suppress additive noise to some degree. To examine the properties of the method proposed, this paper presents an analytical expression for the power spectrum of the deconvolved signals obtained by Kalman Smoothing. This result is then compared to the expectations of relative short time power spectra. Simulations demonstrate the behavior of the deconvolution method in a non-stationary environment.
Guenter, Armin I.
Coherent backscattering in the soft x-ray region
It is shown that coherent polarized soft x-rays can be produced by a combination of two techniques - stimulated amplification of laser light in a magnetic undulator, and Compton scattering of laser photons on an electron beam. In the combined technique, laser radiation is Compton scattered from a relativistic electron beam, whose current or charge density is periodically modulated. An electron beam and a laser beam propagate through an undulator along the same line. Inside the undulator, the laser electromagnetic waste produces a modulation of the electron energy. After some drift space, the modulation of the electron energy transforms into a modulation of the beam longitudinal charge density. The laser photons are reflected by a concave mirror against the electrons and are backscattered. In the process, their energy is greatly increased. If the electron and laser photon energy are matched properly, the modulated electron beam may act as a moving diffraction grating, and the backscattered x-rays show a high degree of coherence. The mechanism of modulation is described. The effects of electron beam energy spread, finite electron beam emittance, and undulator imperfections are discussed. The theory of scattering of a light wave by a bunched electron beam and the properties of the scattered radiation are examined. (LEW)
Matone, G.; Luccio, A.
Statistical moments of backscattered ultrasound in porous fiber reinforced composites.
Statistical moments are important tools for understanding wave propagation in random media and are applied here to backscatter measurements in porous, fiber-reinforced polyimide composites. High temperature resins, such as PMR-15, used in load critical components are much more prone to void production than traditional epoxies. Porosity was induced in thin laminates by cure cycle perturbations and quantified destructively as to void content (0.3 to 8.1%) and radius distribution (10 to 250 mum). Measurements of the statistical moments of the scattered field were made using a single, large aperture transducer. Backscatter signals were acquired and used to calculate the rectified ensemble average, and the point signal-to-noise ratio. The lateral and axial full-width half-maximum (FWHM) were extracted from a two-dimensional auto-covariance of the field and compared to the limiting values set by the diffraction pattern and bandwidth of the measurement transducer. Results confirm that the statistical behavior of the echo amplitudes from porous fabric laminates follow predictions based on circular Gaussian statistics for void contents in the range 2 to 5%. Deviations from these predictions occur for void contents outside this range primarily due to changes in the void distribution. These results are important to the development of better void content measurement techniques and are particularly crucial when imaging specularly reflecting defects embedded in a porous volume because spatial and contrast resolution are limited by speckle and the image signal-to-noise. PMID:18244181
Grolemund, D; Tsai, C S
Combined nano-SIMS/AFM/EBSD analysis and atom probe tomography, of carbon distribution in austenite/?-martensite high-Mn steels.
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
Growth and Rutherford backscattering spectrometry study of direct current sputtered indium oxide films
In2O3 thin films were grown by direct current reactive sputtering. Structural investigations using X-ray diffraction and transmission electron microscopy confirmed the single-phase and polycrystalline nature of the films. Rutherford backscattering spectrometry study of the interface of In2O3 films with Si indicated the formation of ?20 nm thick intermediate region consisting of silicon, oxygen and indium. Annealing at 875 K in
P. Malar; Bhaskar Chandra Mohanty; S. Kasiviswanathan
the importance of x-ray powder diffraction as an analytical tool for phase identification of materials was first pointed out by Debye and Scherrer in Germany and, quite independently, by Hull in the US. Three distinct periods of evolution lead to ubiquitous application in many fields of science and technology. In the first period, until the mid-1940`s, applications were and developed covering broad categories of materials including inorganic materials, minerals, ceramics, metals, alloys, organic materials and polymers. During this formative period, the concept of quantitative phase analysis was demonstrated. In the second period there followed the blossoming of technology and commercial instruments became widely used. The history is well summarized by Parrish and by Langford and Loueer. By 1980 there were probably 10,000 powder diffractometers in routine use, making it the most widely used of all x-ray crystallographic instruments. In the third, present, period data bases became firmly established and sophisticated pattern fitting and recognition software made many aspects of powder diffraction analysis routine. High resolution, tunable powder diffractometers were developed at sources of synchrotron radiation. The tunability of the spectrum made it possible to exploit all the subtleties of x-ray spectroscopy in diffraction experiments.
Hart, M.
Backscattered electron detection in environmental SEM.
An examination of the backscattered electron imaging status in environmental scanning electron microscopy is presented with particular attention to the testing and use of cerium doped yttrium aluminium garnet and yttrium aluminium perovskite scintillation detectors. A comparison is made with plastic scintillating backscattered electron detectors used previously (Nuclear Enterprises type NE102A scintillator). Semi-disk, strip and wedge shapes of these materials have been tested in conjunction with various light-guide geometries. These systems have been combined with two different types of photomultipliers, which also play a critical role in the total detector efficiency. The advantage of increased light output from the monocrystal materials is gained only if matched with suitable light-guides and photomultipliers. The associated problems are discussed and proposals for further work are made for the construction of most efficient backscattered electron detectors in the environmental scanning electron microscope. PMID:22044175
Danilatos, G D
Bathymetry and acoustic backscatter: Estero Bay, California
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.
EBSD characterisation of Y2Ba4CuUOx phase in melttextured YBCO with addition of depleted uranium oxide
NASA Astrophysics Data System (ADS)
Melt-textured YBCO samples processed with added Y2O3 and depleted uranium oxide (DU) contain nano-particles, which have been identified previously as Y2Ba4CuUOx (U-411). This phase has a cubic unit cell, which is clearly distinct from the orthorhombic Y-123 and Y-211 phases within the YBCO system. In samples with a high amount of DU addition (0.8 wt-% DU), U-2411 particles have sizes between 200 nm and several Ąm, so identification of the Kikuchi patterns of this phase becomes possible. Together with a parallel EDX analysis, the particles embedded in the Y-123 matrix can be identified unambiguously. In this way, a three-phase EBSD scan becomes possible, allowing also the identification of nanometre-sized particles in the sample microstructure.
Koblischka-Veneva, A.; M³cklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.
Backscattered polarimetric detection from biological tissue
In this study, backscattering optical measurements from this scattering media and biological tissue were performed using different polarimetric detection techniques. The outcome of this study may facilitate the early diagnosis, monitoring, and assessment of disease progress, with high sensitivity and specificity.
G. C. Giakos; S. Marotta; K. Ambadipudi; K. Valluru; J. Petermann; C. Narayan; D. Natarajamani; D. Pingili; D. B. Sheffer; M. G. Kounelakis; G. Livanos; M. E. Zervakis
Snowcover influence on backscattering from terrain
NASA Technical Reports Server (NTRS)
The effects of snowcover on the microwave backscattering from terrain in the 8-35 GHz region are examined through the analysis of experimental data and by application of a semiempirical model. The model accounts for surface backscattering contributions by the snow-air and snow-soil interfaces, and for volume backscattering contributions by the snow layer. Through comparisons of backscattering data for different terrain surfaces measured both with and without snowcover, the masking effects of snow are evaluated as a function of snow water equivalent and liquid water content. The results indicate that with dry snowcover it is not possible to discriminate between different types of ground surface (concrete, asphalt, grass, and bare ground) if the snow water equivalent is greater than about 20 cm (or a depth greater than 60 cm for a snow density of 0.3 g/cu cm). For the same density, however, if the snow is wet, a depth of 10 cm is sufficient to mask the underlying surface.
Ulaby, F. T.; Abdelrazik, M.; Stiles, W. H.
Backscatter in the rational LES model.
This paper presents a comparison for the backscatter (the inverse transfer of energy from small to large scales) in the rational and the gradient large eddy simulation (LES) models. We applied both LES models in the numerical simulation of turbulent channel flows at Re{sub T} = 180 and 395. The rational LES model yielded improved results and was more stable numerically.
Iliescu, T.; Fischer, P.; Mathematics and Computer Science
Reduction of Backscattering by Impedance Loading.
National Technical Information Service (NTIS)
Reduction of nonspecular backscatter from a thin square conducting plate with the leading edge parallel to the electric field by impedance loading is studied in this report. The plate is modeled with a wire-grid structure. With a thin-wire computer progra...
C. W. Chuang
Terahertz backscattering behavior of various absorbing materials
The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15░ to 75░. In addition to the backscattering behavior, the
C. Wu; A. J. Gatesman; L. Deroeck; T. Horgan; R. H. Giles; W. E. Nixon
Radar Backscatter from Conducting Polyhedral Spheres
Electromagnetic backscatter characteristics of conducting polyhedral spheres, constructed of 12 pentagons and a large number of hexagons, were investigated. The polyhedral structures were classified by their number of vertices and by the width of the conducting edges in their frames. Polyhedral spheres with 60, 80, 180, 240, 320, 500, 540, 960, and 1500 vertices were evaluated for their ability to
Paul A. Bernhardt
Simulation of ultrasound backscatter images from fish
The objective of this work is to investigate ultrasound (US) backscatter in the MHz range from fish to develop a realistic and reliable simulation model. The long term objective of the work is to develop the needed signal processing for fish species differentiation using US. In in-vitro experiments, a cod (Gadus morhua) was scanned with both a BK Medical ProFocus
An Hoai Pham; Bjarne Stage; Martin Christian Hemmsen; Bo Lundgren; Mads M°ller Pedersen; Tina Bock Pedersen; J°rgen Arendt Jensen
Non-vacuum Rutherford backscattering spectrometry
External beams of high energy protons (3 to 6 MeV) and alpha particles (10 MeV) have for the first time been used successfully for Rutherford Backscattering Spectrometry depth profiling. This new capability permits the analysis of objects which are too large or otherwise incompatible with an accelerator vacuum system. Preliminary tests of this system indicate the potential for a depth
B. Doyle
Characterization of a ?-backscattering imaging device
NASA Astrophysics Data System (ADS)
The Compton Camera is a ?-backscattering imaging device that allows us to obtain images of hidden objects. In order to evaluate the factors that affect the quality of those images, experiments were carried out to determine its response to different materials. Mathematical methods have been developed to quantify the image quality.
Gonzßlez, N.; Fajardo, E.; Blanco, W.; Cristancho, F.
Study of Laser Backscatter by Particulates in Stack Emissions.
National Technical Information Service (NTIS)
The validity of determining smoke plume opacity or particulate content from measurements of the backscatter of laser radiation from plume particulates was investigated. The backscatter experiments were conducted with the use of a specially designed aeroso...
E. E. Uthe C. E. Lapple
Analysis of the backscatter spectrum in an ionospheric modification experiment
NASA Technical Reports Server (NTRS)
Predictions of the backscatter spectrum, including effects of ionospheric inhomogeneity, are compared with experimental observations of incoherent backscatter from an artificially heated region. Our calculations show that the strongest backscatter echo received is not from the reflection level, but from a region some distance below. Certain asymmetrical features are explained of the up-shifted and down-shifted plasma lines in the backscatter spectrum, and the several satellite peaks accompanying them.
Kim, H.; Crawford, F. W.; Harker, K. J.
Methods for the accurate analysis of channeling Rutherford backscattering spectrometry
The accuracy of quantitative analysis of disorder profiles in monocrystalline solids by using Rutherford backscattering spectrometry has been limited by the issues that: (1) the stopping power of channeled and nonchanneled particles differ substantially; (2) the backscattering of channeled particles from displaced atoms is hard to separate from the backscattering of dechanneled particles. In this study, we have developed a
Lin Shao; Michael Nastasi
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.
Terahertz backscattering behavior of various absorbing materials
NASA Astrophysics Data System (ADS)
The Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has investigated the electromagnetic scattering behavior of various broadband absorbers. Several absorbing materials were tested in a compact radar range operating at a center frequency of 160 GHz. The polarimetric radar cross section was measured at elevation angles from 15░ to 75░. In addition to the backscattering behavior, the normal incidence transmittance of the materials was evaluated.
Wu, C.; Gatesman, A. J.; Deroeck, L.; Horgan, T.; Giles, R. H.; Nixon, W. E.
Backscattering measurement from a single microdroplet.
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
Low-Frequency Electromagnetic Backscattering from Tunnels
Low-frequency electromagnetic scattering from one or more tunnels in a lossy dielectric half-space is considered. The tunnel radii are assumed small compared to the wavelength of the electromagnetic field in the surrounding medium; a tunnel can thus be modeled as a thin scatterer, described by an equivalent impedance per unit length. We examine the normalized backscattering width for cases in which the air-ground interface is either smooth or rough.
Casey, K; Pao, H
Backscattering Measurement From a Single Microdroplet
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.
Lee, Jungwoo; Chang, Jin Ho; Jeong, Jong Seob; Lee, Changyang; Teh, Shia-Yen; Lee, Abraham; Shung, K. Kirk
Backscattering Cross Section of Ultrawideband Antennas
Backscattering of ultrawideband (UWB) antennas is theoretically and experimentally studied in this letter. The finite-difference time-domain (FDTD) method using Berenger's perfectly matched layer absorbing boundary condition (PML-ABC) is employed for simulation and the measurement is carried out in indoor environment. Monostatic radar cross section (RCS) of square-slot antenna and printed circular-disc monopole antenna (PCDMA) terminated with three different kinds of
Sanming Hu; Honghui Chen; C. K. Law; Z. Shen; L. Zhu; W. Zhang; W. Dou
Estimating splash pine biomass using radar backscatter
L-band HV multiple-incidence-angle aircraft synthetic aperture radar (SAR) data were analyzed in relation to average stand biomass, basal area, and tree height for 55 slash pine plantations located in northern Florida. This information was used to develop a system of equations to predict average stand biomass as a function of L-band (24.5-cm) radar backscatter. The system of equations developed in
Yousif Ali Hussin; Robin M. Reich; Roger M. Hoffer
Automatic analysis of Rutherford backscattering spectrometry spectra
It has been shown that Bayesian statistics is a powerful tool in the analysis of ion beam analysis (IBA) data. Past work has shown its applicability to the deconvolution of the detector response function from micro-Rutherford backscattering spectrometry (RBS) and micro-proton-induced X-ray emission (PIXE) spectra, subtraction of the background from PIXE spectra, the extraction of depth profiles from PIXE spectra
J. Padayachee; K. A. Meyer; V. M. Prozesky
Bomb detection using backscattered x rays
NASA Astrophysics Data System (ADS)
Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sites of the package. This poses a problem if the package is placed so that only one side is accessible, such as against a wall. There is also a threat to personnel and property since explosive devices may be 'booby trapped.' We have developed a method to x-ray a package using backscattered x-rays. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. When an object is subjected to x-rays, some of them are scattered back toward the source. The backscattering of x-rays is proportional to the atomic number (Z) of the material raised to the 4.1 power. This Z4.1 dependence allows us to easily distinguish between explosives, wires, timer, batteries, and other bomb components. Backscatter experiments at Sandia National Laboratories have been conducted on mock bombs in packages. We are able to readily identify the bomb components. The images that are obtained in this procedure are done in real time and the image is displayed on a computer screen.
Lockwood, Grant J.; Shope, Steve L.; Wehlburg, Joseph C.; Selph, Michael M.; Jacobs, Jennifer
Electron back scattered diffraction (EBSD) analysis of quasi-cleavage and hydrogen induced fractures under cyclic and dwell loading in titanium alloys
Evidence for sub-surface fatigue crack initiation is often reported for near alpha titanium alloys such as the coarse grained IMI685 and the fine duplex structured IMI834. In such materials with a typical as received hydrogen concentration of 40¢60 ppm the initiation site is invariably characterized by quasi-cleavage facetting. Similar facetting is also associated with the low temperature dwell sensitive fatigue
Orientation relationship in various 9%Cr ferritic\\/martensitic steels¢EBSD comparison between Nishiyama¢Wassermann, Kurdjumov¢Sachs and Greninger¢Troiano
EBSD measurements were carried out on four different martensitic steels (T91, P92, EM10 and Eurofer) in various metallurgical conditions (nine different microstructural states). The usual orientation relationships (ORs) between the parent austenitic phase and the resulting martensite in martensitic steels are those of Nishiyama¢Wassermann (NW) and Kurjumov¢Sachs (KS). The present study first proposes a methodology based on the combined analysis
F. Barcelo; J.-L. Bechade; B. Fournier
GLObal Backscatter Experiment (GLOBE) results: Aerosol backscatter global distribution and wavelength dependence
NASA Technical Reports Server (NTRS)
The GLObal Backscatter Experiment (GLOBE) was initiated by NASA in 1986 as an interagency and international research effort to characterize tropospheric backscatter properties. The primary objective of the program is to develop realistic aerosol backscatter inputs for design and simulation studies for NASA's prospective Laser Atmospheric Wind Sounder (LAWS). To achieve this, GLOBE incorporates several different types of aerosol sensors, which operate from a variety of sensor platforms, covering a wide range of spatial and temporal scales, and measure a diverse set of aerosol physical, chemical, and optical properties. The results of this analysis have provided important new information on the life cycles and physicochemical properties of global scale tropospheric aerosol systems. In addition, GLOBE analytical methods will be useful for the Earth Observing System (EOS) and other studies that involve the assimilation of large, complex atmospheric aerosol databases.
Bowdle, David A.
Examination of lower Jurassic mudrocks using backscattered electron microscopy
The small size of many of the particles in mudrocks makes it almost impossible to image and identify them individually and in situ, using conventional light microscopy. Since the average mudrock contains about 60% clay minerals, an understanding of these minerals is central to the question of burial diagenesis and hydrocarbon generation. Much of the existing evidence concerning burial diagenesis relies on x-ray diffraction data (XRD), particularly with respect to the clay-sized (< 2 ..mu..m) fraction of mudrocks. Backscattered electron techniques (BSE) in scanning electron microscopy (SEM) together with energy-dispersive x-ray microanalysis (EDX), XRD, and electron microprobe analysis, indicate that Lower Jurassic mudrocks from the North Sea basin contain many clay mineral stacks up to 150 ..mu..m long. By studying polished mudrock sections with BSE and EDX, the sizes, shape, orientation, textural relations and internal compositional variation of the clay minerals can be observed in situ. Preliminary evidence suggests that the clay stacks are authigenic and may have formed at shallow burial depths during early diagenesis. In addition, sand- and silt-sized clay pellets (glauconite) composed chiefly of iron-bearing dioctahedral mica were observed in the sediment. The irregular shapes and textural intergrowths of many pellets suggest that active outward growth occurred, probably by a combination of displacement and replacement in the surrounding matrix material.
Krinsley, D.; Pye, K.
Backscattering Differential Ghost Imaging in Turbid Media
NASA Astrophysics Data System (ADS)
In this Letter we present experimental results concerning the retrieval of images of absorbing objects immersed in turbid media via differential ghost imaging (DGI) in a backscattering configuration. The method has been applied, for the first time to our knowledge, to the imaging of thin black objects located inside a turbid solution in proximity of its surface. We show that it recovers images with a contrast better than standard noncorrelated direct imaging, but equivalent to noncorrelated diffusive imaging. A simple theoretical model capable of describing the basic optics of DGI in turbid media is proposed.
Bina, M.; Magatti, D.; Molteni, M.; Gatti, A.; Lugiato, L. A.; Ferri, F.
Correlations between microstructure and backscattered ultrasonic energy
NASA Astrophysics Data System (ADS)
Copper, Ni, and Monel samples were cold-worked and then annealed to produce a wide range of anisotropic and equiaxed microstructures. Samples of these materials were excited by surface waves and by shear waves using a high-frequency focused transducer in immersion tests. Backscattered waveforms were collected, and analyzed with several signal processing techniques, including stacked A-scans, variance calculations, DFTs, and calculations of the DFT variance. Each processing technique was found to produce results which can be correlated with microstructural variations. However, an absolute measure of grain size or grain boundary stiffness has not been identified.
Mittleman, John; Mohr, David W.
Modeling canopy reflectance and microwave backscattering coefficient
NASA Technical Reports Server (NTRS)
Various approaches to model canopy reflectance (CR) in the visible/infrared region and backscattering coefficient (BSC) in the microwave region are compared and contrasted. It is noted that BSC can be related to CR in the source direction (the 'hot spot' direction). By assuming a frequency dependent leaf reflectance and transmittance it is shown that the observed dependence of BSC on leaf area index, leaf angle distribution, angle of incidence, soil moisture content, and frequency can be simulated by a CR model. Thus both BSC and CR can, in principle, be calculated using a single model which has essentially the same parameters as many CR models do.
Goel, N. S.
[Influence of petroleum concentration in water on spectral backscattering coefficient].
The petroleum pollutants mixing proportion experiment and in-situ experiment were carried out in the estuary of Panjin, Liaoning province in May 2008 and August 2009. The optical properties and biochemical properties were measured to get the effect of petroleum concentration in water on backscattering coefficients spectrum. The results show that the power-law index of backscattering coefficient decreases as TSM concentration increases and the relationship of these variables follows logarithm mode. Specific backscattering coefficient's value of 440 to 856 nm is between 0.006 and 0.035 m2 x g(-1) and decreases as wavelength increases. The petroleum mass-specific backscattering coefficients (backscattering coefficients of unit petroleum concentration) decreases with the wavelength increasing and follows power law for petroleum concentration. Petroleum concentration has little effect on the power-law index of backscattering coefficient. PMID:21105413
Song, Qing-jun; Huang, Miao-fen; Tang, Jun-wu; Wang, Xiao-mei
Uniqueness for the inverse backscattering problem for angularly controlled potentials
NASA Astrophysics Data System (ADS)
We consider the problem of recovering a smooth, compactly supported potential on { {R}}^3 from its backscattering data. We show that if two such potentials have the same backscattering data and the difference of the two potentials has controlled angular derivatives, then the two potentials are identical. In particular, if two potentials differ by a finite linear combination of spherical harmonics with radial coefficients and have the same backscattering data then the two potentials are identical.
Rakesh; Uhlmann, Gunther
Sea Floor Analyses Based On Multibeam Backscatter Strength
NASA Astrophysics Data System (ADS)
Measurements of acoustic backscatter strength can be applied to analyse sea floor coverage on a spatial extent. They provide consistent coverage compared to analy- ses based on only a few surface samples. In particular the spatial validity of surface samples can be determined by analyses based on acoustic backscatter strength and sampling locations representative for the surrounding area can be determined. Dur- ing the cruise ANTXVII/4 of the German RV "Polarstern", a high precision swath bathymetry survey was performed along the European continental margin in the Por- cupine Seabight off southwest Ireland. Within the Porcupine Seabight a number of mound structures have been discovered earlier, most of them being carbonate mounds. The structure and genesis of these mounds are the main objective of recent investiga- tions. The cruise and the subsequent investigations are part of the EU project GEO- MOUND. They focus on the Belgica mound province. Besides the depth measure- ments, the acoustic intensities of the received echos have been recorded. Taking into account the transmitted and received sound level, acoustic beam patterns, and acous- tic attenuation in the water column, the backscatter strength of the ensonified area was calculated. This backscatter information is used to analyse the sea floor cover- age. Based on the data of the systematic survey the spatial variation of the backscatter strength was derived. Regions of equal backscatter characteristic can be combined and functions showing the dependency between backscatter strength and incidence angle of the acoustic wave can be determined. These functions help interpreting sea floor coverage. The mapping of the backscatter strength of the mound area indicates clear changes in backscatter strength. Small and shallow channels show a lower backscat- ter strength than their surroundings. That means the surface coverage of the channels is smooth with respect to the surroundings. One interpretation of this surface pattern points to currents that have built these structures by depositing sediments. In con- trast, most of the mounds indicate a strong backscatter strength. Since other investi- gations showed that some of the mounds are populated by corals, these corals could cause higher backscatter strength. A detailed investigation of the mounds indicates differences of backscatter characteristics between them. There are mounds that show strong backscatter on their slopes but low backscatter on their top. Other mounds show stronger backscatter on their top but lower backscatter on their slopes. These differences could indicate varying surface coverage of those mounds. Based on this information, the mounds are separated and classified.
Beyer, A.
A predictive model of backscattering at subdiffusion length scales
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-Matķrn 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.
Turzhitsky, Vladimir; Radosevich, Andrew; Rogers, Jeremy D.; Taflove, Allen; Backman, Vadim
Rotational Raman scattering (Ring effect) in satellite backscatter ultraviolet measurements
NASA Astrophysics Data System (ADS)
A detailed radiative transfer calculation has been carried out to estimate the effects of rotational Raman scattering (RRS) on satellite measurements of backscattered ultraviolet radiation. Raman-scattered light is shifted in frequency from the incident light, which causes filling in of solar Fraunhofer lines in the observed backscattered spectrum (also known as the Ring effect). The magnitude of the rotational Raman scattering filling in is a function of wavelength, solar zenith angle, surface reflectance, surface pressure, and instrument spectral resolution. The filling in predicted by our model is found to be in agreement with observations from the Shuttle Solar Backscatter Ultraviolet Radiometer and the Nimbus-7 Solar Backscatter Ultraviolet Radiometer.
Cebula, Richard P.; Joiner, Joanna; Bhartia, Pawan K.; Hilsenrath, Ernest; McPeters, Richard D.; Park, Hongwoo
Compton backscattered collimated x-ray source
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.
Compton backscattered collimated x-ray source
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)
Compton backscattered collmated X-ray source
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)
Simulation of ultrasound backscatter images from fish
NASA Astrophysics Data System (ADS)
The objective of this work is to investigate ultrasound (US) backscatter in the MHz range from fish to develop a realistic and reliable simulation model. The long term objective of the work is to develop the needed signal processing for fish species differentiation using US. In in-vitro experiments, a cod (Gadus morhua) was scanned with both a BK Medical ProFocus 2202 ultrasound scanner and a Toshiba Aquilion ONE computed tomography (CT) scanner. The US images of the fish were compared with US images created using the ultrasound simulation program Field II. The center frequency of the transducer is 10 MHz and the Full Width at Half Maximum (FWHM) at the focus point is 0.54 mm in the lateral direction. The transducer model in Field II was calibrated using a wire phantom to validate the simulated point spread function. The inputs to the simulation were the CT image data of the fish converted to simulated scatter maps. The positions of the point scatterers were assumed to be uniformly distributed. The scatter amplitudes were generated with a new method based on the segmented CT data in Hounsfield Units and backscatter data for the different types of tissues from the literature. The simulated US images reproduce most of the important characteristics of the measured US image.
Pham, An Hoai; Stage, Bjarne; Hemmsen, Martin Christian; Lundgren, Bo; Pedersen, Mads M°ller; Pedersen, Tina Bock; Jensen, J°rgen Arendt
An Efficient Image Recovery Algorithm for Diffraction Tomography Systems
NASA Technical Reports Server (NTRS)
A diffraction tomography system has potential application in ultrasonic medical imaging area. It is capable of achieving imagery with the ultimate resolution of one quarter the wavelength by collecting ultrasonic backscattering data from a circular array of sensors and reconstructing the object reflectivity using a digital image recovery algorithm performed by a computer. One advantage of such a system is that is allows a relatively lower frequency wave to penetrate more deeply into the object and still achieve imagery with a reasonable resolution. An efficient image recovery algorithm for the diffraction tomography system was originally developed for processing a wide beam spaceborne SAR data...
Jin, Michael Y.
Effect of Frequency on the Change in Backscattered Ultrasound Energy as a Function of Temperature
NASA Astrophysics Data System (ADS)
Clinical trials have demonstrated that hyperthermia improves cancer treatments. Previous studies have developed temperature imaging methods based on the change in the backscattered energy (CBE) of ultrasound in order to monitor temperature variations during hyperthermia. The CBE with temperature is primarily due to the temperature dependency of the backscattering coefficient, which largely depends on the ultrasound frequency. This study explored the effect of frequency on the CBE as a function of temperature. Phantom experiments involving uniform heating from 37 to 45 ░C were carried out in a temperature-regulated water tank, and the raw backscattered signals were acquired using ultrasound transducers with center frequencies of 5, 10, and 15 MHz for CBE imaging. The compensation of echo shift due to temperature increase was not made for simplifying the algorithm. In the condition without motion compensation, the results showed that the absolute value of the CBE (ACBE) increases with increasing temperature. The dynamic range of the ACBE at the focus of the transducer between 37 and 45 ░C increased from 5.6 to 10 dB when the ultrasound frequency increased from 5 to 15 MHz, demonstrating that the sensitivity of the CBE image in indicating the temperature variation may increase with the ultrasound frequency. However, the dynamic range of the ACBE over the same temperature range increased from only 5.5 to 6.2 dB when the CBE data were acquired from the far field of the transducer. This indicates that the beam diffraction of the transducer may reduce the dependence of the CBE on frequency, suggesting that the beam diffraction effect should be taken into account when CBE imaging employs a high-frequency transducer for sensitive temperature detection.
Tsui, Po-Hsiang; Chien, Yu-Ting
Coherent backscattering of turbid samples containing large Mie spheres
NASA Astrophysics Data System (ADS)
We found that the coherent backscattering cone of turbid samples containing spherical Mie scatterers with a size parameter larger than about 20 strongly deviates from known analytical curve shapes. We compare experimental data with numerical simulations of Monte Carlo type. Moreover, we present a new wide-angle coherent backscattering set-up.
Lenke, Ralf; Tweer, Ralf; Maret, Georg
Near-Nadir Radar Backscatter From Ocean Waves
NASA Technical Reports Server (NTRS)
Paper discusses aspects of theory of near-nadir radar backscatter from well-developed sea. Study contributed to development of new technique for determination of sea-state bias in satellite altimeter measurements. Paper questions assumptions, bringing accepted interpretation of nadir and near-nadir radar backscattering into doubt.
Glazman, Roman E.
Integrated backscatter for quantification of left atrial spontaneous echo contrast
Objectives. This study was designed to develop a quantitative method of spontaneous echo contrast (SEC) assessment using integrated backscatter and to compare integrated backscatter SEC measurement with independent qualitative grades of SEC and clinical and echocardiographic predictors of thromboembolism.Background. Left atrial SEC refers to dynamic swirling smoke-like echoes that are associated with low flow states and embolic events and have
Allan L. Klein; R. Daniel Murray; Ian W. Black; Shalabh Chandra; Richard A. Grimm; Alwyn P. D'Sa; Dominic Y. C. Leung; David Miller; Annitta J. Morehead; Susan E. Vaughn; James D. Thomas
Radar Waveform Design for Low Power Monostatic Backscattering Ionosonde
\\u000a This paper introduces radar waveform design for a low power monostatic backscattering ionosonde. Bi-phase interpulse coded\\u000a pulse train is analyzed. The waveform can achieve high pulse compression gain, long unambiguous range, highrange resolution\\u000a and high Doppler resolution, and are specially suitable for low power monostatic backscattering ionosonde.
Ming Yao; Zhengyu Zhao; Bo Bai; Xiaohua Deng; Gang Chen; Shipeng Li; Fanfan Su
Radar backscattering properties of nonspherical ice crystals at 94 GHz
The millimeter wavelength radar backscattering properties at 94 GHz for six nonspherical ice crystals, which include hexagonal column, hollow, plate, bullet rosette, aggregate, and droxtal with 46 maximum dimensions ranging from 2 to 10,500 mum, are investigated using the discrete dipole approximation (DDA) method and Lorenz-Mie theory. It is found that the radar backscattering cross sections are sensitive to ice
Gang Hong
Radar backscattering properties of nonspherical ice crystals at 94 GHz
The millimeter wavelength radar backscattering properties at 94 GHz for six nonspherical ice crystals, which include hexagonal column, hollow, plate, bullet rosette, aggregate, and droxtal with 46 maximum dimensions ranging from 2 to 10,500 ?m, are investigated using the discrete dipole approximation (DDA) method and Lorenz-Mie theory. It is found that the radar backscattering cross sections are sensitive to ice
Gang Hong
Radar observations of strong subsurface scatterers. A model of backscattering
Backscattering from strong buried scatterers (like water and gas mains) are studied both experimentally and theoretically. The contrast coefficients are introduced as a quantitative characteristics of the relative contribution of subsurface strong reflector to backscattered signal against the background of scattering of air-soil interface. Even though the radar response from ōidealö subsurface body itself is negligibly small, scattering from roughness
A. Kalmykov; I. Fuks; I. Scherbinin; V. Tsymbal; A. Matveev; A. Gavrilenko; M. Fix; V. Freilikher
A method for removing arm backscatter from EPID images
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)
SEM/EDS/EBSD study of the behaviour of Ge, Mo and Al impurities in complex-doped crystals of higher manganese silicide
NASA Astrophysics Data System (ADS)
The structure of Al, Ge, Mo doped higher manganese silicides (HMS) grown by the Bridgman technique has been studied by SEM/EDS/EBSD methods. It is shown that dopants are partially integrated into the HMS crystal lattice. Some inclusions with sizes of 0.1-100 ?m and different shapes (round, irregular, elongated) are formed. The precipitation of tetragonal MoSi2 and Si-Ge solid-solution has been observed. MoSi2 inclusions hundreds of microns in size form a multicomponent texture. The inclusions of Si-Ge solid solution have an irregular shape. The orientation relationship between these inclusions and matrix crystal is determined.
Orekhov, A. S.; Solomkin, F. Y.
Effect of Overburden Thickness on the Copper Microstructure of Dual-Inlaid Interconnect Structures
Dual-inlaid Cu interconnects with different overburden thicknesses were fabricated and subsequently annealed applying identical conditions. The microstructure in trenches was characterized by electron backscatter diffraction (EBSD) before and after chemical mechanical polishing (CMP). For samples subjected to CMP, grain size and texture were determined from top-view EBSD scanning on arrays of trenches. Smaller grain size and stronger Cu (111) texture were observed in the samples with thinner overburden layer. Further EBSD investigations were carried out on cross-sections of trenches in samples not subjected to CMP which suggested interplay of grain growth mechanism in trench and overburden.
Yan, M. Y. [AMD Saxony LLC and Co. KG, Wilschdorfer Landstr. 101, 01109 Dresden (Germany); Department of Materials Science and Engineering, UCLA, Los Angeles, CA 90095-1595 (United States); Tu, K. N. [Department of Materials Science and Engineering, UCLA, Los Angeles, CA 90095-1595 (United States); Vairagar, A. V.; Meyer, M. A.; Geisler, H.; Preusse, A.; Zschech, E. [AMD Saxony LLC and Co. KG, Wilschdorfer Landstr. 101, 01109 Dresden (Germany)
Plastic strain characterization in austenitic stainless steels and nickel alloys by electron backscatter diffraction
Stress corrosion cracking (SCC) is enhanced by cold work and causes many problems in components of the nuclear power plants. Besides, during manufacturing, installation, welding and service of the material, residual strains can be produced increasing the susceptibility to SCC. For this reason, it is important to characterize the degree of plastic strain due to dislocation accumulation in each crystal.
A. Sßez-Maderuelo; L. Castro; G. de Diego
Metallographic Preparation of Space Shuttle Reaction Control System Thruster Electron Beam Welds for Electron Backscatter Diffraction.
National Technical Information Service (NTIS)
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 crac...
J. Martinez
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.
National Technical Information Service (NTIS)
Significant progress has been made toward solving the century-old problem of chromatic aberrations in diffractive optics. Our approach exploits modern materials and microfabrication technology and is very different from the 'purely diffractive strategy', ...
N. M. Ceglio A. M. Hawryluk D. P. Gaines R. A. London L. G. Seppala
National Technical Information Service (NTIS)
Significant progress has been made toward solving the century-old problem of chromatic aberrations in diffractive optics. Our approach exploits modern materials and microfabrication technology and is very different from the ''purely diffractive strategy,'...
A. M. Hawryluk D. P. Gaines L. G. Seppala N. M. Ceglio R. A. London
Direction angle sensitivity of agricultural field backscatter with AIRSAR data
NASA Technical Reports Server (NTRS)
This paper presents a study of the direction angle sensitivity of radar backscatter from agricultural fields. The direction angle is defined as the angle between the incident plane and the perpendicular to the field row direction. Previous studies have concentrated on comparing the backscatter of agricultural fields imaged with 0, 45, and 90 degree direction angles. In contrast, this study concentrates on the backscatter changes occurring when the direction angle is modified by a few degrees or even by fractions of a degree. This is possible by using the output of the NASA/JPL AIRSAR processor, in which sixteen independent frames are formed, each one corresponding to the same radar scene imaged with a slightly different squint angle. The studied data set is an agricultural area in La Mancha, Spain acquired in June and July 1991 during the EFEDA experiment. This paper describes the observed backscatter variations of the agricultural fields with direction angle measured at P, L, and C bands. As expected, the backscatter is maximum for a 0 degree direction angle. For several fields, the backscatter at P and L bands drops by more than 10 dB for a 5 degree change in direction angle. Furthermore, the sensitivity to the direction angle decreases with increasing vegetation. The variations in backscatter are compared with model predictions. One model, which agrees with scatterometer data, underestimates the observed backscatter variations with direction angle by more than 10 dB. It does not take into account the possible coherent component of the radar signal. We believe the strong direction sensitivity of agricultural field backscatter obtained with SAR data is due to a Bragg resonant effect, resulting in a strong coherent return when the direction angle is zero. The observations are then projected to the case of spaceborne SAR data.
Dubois, Pascale C.; Rignot, Eric; Vanzyl, Jakob J.
Higher-order acoustic diffraction by edges of finite thickness.
A cw solution of acoustic diffraction by a three-sided semi-infinite barrier or a double edge, where the width of the midplanar segment is finite and cannot be ignored, involving all orders of diffraction is presented. The solution is an extension of the asymptotic formulas for the double-edge second-order diffraction via amplitude and phase matching given by Pierce [A. D. Pierce, J. Acoust. Soc. Am. 55, 943-955 (1974)]. The model accounts for all orders of diffraction and is valid for all kw, where k is the acoustic wave number and w is the width of the midplanar segment and reduces to the solution of diffraction by a single knife edge as w-->0. The theory is incorporated into the deformed edge solution [Stanton et al., J. Acoust. Soc. Am. 122, 3167 (2007)] to model the diffraction by a disk of finite thickness, and is compared with laboratory experiments of backscattering by elastic disks of various thicknesses and by a hard strip. It is shown that the model describes the edge diffraction reasonably well in predicting the diffraction as a function of scattering angle, edge thickness, and frequency. PMID:18247730
Chu, Dezhang; Stanton, Timothy K; Pierce, Allan D
Characterization of the backscattered radiation from petawatt laser matter interactions
The development of high peak power and energy laser systems require the assurance that any backscattered radiation will not lead to damage of the laser system. We present the characterization of the backscattered radiation for different target types and conditions at petawatt power levels and intensities (>10{sup 20}W/cm{sup 2}). We observe that radiation is generated between 700 and 900 nm, as well as the expected self emission and laser fundamental. The percentage of the incident light backscattered reduces as a function of the incident energy and is typically <1% for petawatt laser interactions.
Vernon, Edwina D.; Musgrave, Ian O.; Green, James; Heathcote, Robert; Lancaster, Kate L.; Mendes, Cedric; Hawkes, Steve J.; Hernandez-Gomez, Cristina; Pepler, Dave A
Brillouin backscatter model in LASNEX: improvements and additions
In the 1978 Annual Report, a stimulated Brillouin scatter (SBS) model for LASNEX was described. Many improvements and additions have been made in 1979 in order to model the Brillouin backscatter in underdense plasmas more accurately. The density dependence of the model was changed and the effects of inhomogeneous media were included. A self-consistent calculation of the hot ion contribution to the ion damping was added and the saturation calculation and calculation of backscatter when a very small fraction is reflected were improved. Finally, the treatment of the backscattered light has been considerably expanded. In this report, these changes to the SBS model are described.
Harte, J.; Estabrook, K.
The back-scattering problem in three dimensions
In this article we study the (inverse) back-scattering problem for the Schr÷dinger operator in R\\u000a 3. We introduce the back-scattering transform B(v) of a real-valued potential $${v\\\\in C_0^\\\\infty (\\\\mathbf{R} _3)}$$, and prove that the back-scattering data associated to v determine B(v). Under the assumption that the Schr÷dinger operator H\\u000a \\u000a v\\u000a Ā=Ā??+v has no eigenvectors in L\\u000a 2(R\\u000a 3) it is
Robert Lagergren
CO(2) lidar backscatter profiles over Hawaii during fall 1988.
Aerosol and cloud backscatter data, obtained over a 24-day period in fall 1988 with the National Oceanic & Atmospheric Administration's Doppler lidar at 10.59-microm wavelength, are analyzed by using a new technique to lessen biases that are due to dropouts. Typical backscatter cross sections were significantly lower than those routinely observed over the continental United States, although episodic backscatter enhancements caused by cirrus and mineral dust also occurred. Implications of these data on the proposed Laser Atmospheric Wind Sounder wind profiling satellite sensor are discussed. PMID:20725465
Post, M J; Cupp, R E
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
Characteristics of Adaptive Beamforming Methods in an HF Backscatter Environment.
National Technical Information Service (NTIS)
The objective of this program is to investigate the advantages which may accrue to HF backscatter systems employing adaptive beamforming methods. The efforts were directed toward obtaining detailed information regarding the performance of time-domain adap...
L. J. Griffiths
Simulation of coherent backscattering of light in nematic liquid crystals
NASA Astrophysics Data System (ADS)
Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.
Aksenova, E. V.; Kokorin, D. I.; Romanov, V. P.
Rutherford backscattering oscillation in scanning helium-ion microscopy
NASA Astrophysics Data System (ADS)
Scanning helium-ion microscopy (SHIM) yields high-resolution imaging and is capable of surface elemental analysis at the nanometer scale. Here we examine recently discovered SHIM backscattered intensity oscillations versus the target atomic number. These oscillations are contrary to the expected monotonic increase of the backscattered helium-ion (He+) rate with the atomic number of elemental samples. We explore the ion-sample interaction via numerical simulations for a variety of scattering geometries and confirm the presence of oscillations. The oscillations are attributed to the atomic rather than the nuclear structure of the target. To that end, we study the link (near anticorrelation) between backscatter rate and He+ beam stopping power, both versus the target atomic number. This leads us to ascribe the origin of the backscatter oscillation to the ``Z2-oscillations'' of the stopping power in ion-beam physics, with the latter being rooted in the valence electron configuration of elemental targets.
Kostinski, Sarah; Yao, Nan
Moessbauer Backscatter Spectrometer with Full Data Processing Capability.
National Technical Information Service (NTIS)
The design and operation of a Moessbauer backscatter spectrometer with full data processing capability is described, and the investigation of the applicability of this technique to a variety of practical metallurgical problems is discussed. (ERA citation ...
Coherent backscattering of light in nematic liquid crystals
Multiple light scattering by director fluctuations in nematic liquid crystals is considered. A uniform director orientation is assumed to be specified by an applied magnetic field. The coherent backscattering effect, which consists in the presence of a sharp light backscattering peak, is studied. The Bethe-Salpeter equation is used to calculate the multiple scattering intensity taking into account the contributions of ladder and cyclic diagrams. An analytical expression for the angular and polarization dependences of the coherent backscattering intensity is obtained in terms of the diffusion approximation. The calculation and experimental results are compared. The developed theory is shown to qualitatively describe the elliptical shape of the backscattering cone, to explain the absence of a coherent contribution for crossed polarizations, and to calculate the relative peak height.
Aksenova, E. V. [St. Petersburg State University (Russian Federation)], E-mail: firstname.lastname@example.com; Kuz'min, V. L. [St. Petersburg Institute of Trade and Economics (Russian Federation); Romanov, V. P. [St. Petersburg State University (Russian Federation)
Compton backscattering polarimeter for measuring longitudinal electron polarization.
National Technical Information Service (NTIS)
Compton backscattering polarimetry provides a fast measurement of the polarization of an electron beam in a storage ring. Since the method is non-destructive, the polarization of the electrons can be monitored during internal target experiments. At NIKHEF...
I. Passchier D. W. Higinbotham N. Vodinas N. Papadakis K. de Jager
BASIS: A New Backscattering Spectrometer at the SNS
A new spectrometer named BASIS has recently entered the general user program at the Spallation Neutron Source. BASIS is an acronym for Backscattering Silicon Spectrometer. While there are several operational reactor-based spectrometers that utilize backscattering reflection from silicon single crystals, such as IN10 and IN16 [1] at the ILL, France; HFBS [2] at the NCNR, USA; and SPHERES [3] at the FRM-II, JCNS, Germany, BASIS is the first silicon backscattering spectrometer built on a spallation neutron source. Conceptually, it is similar to previously built time-of-flight backscattering spectrometers that utilize reflections from pyrolytic graphite or mica, such as IRIS [4] and OSIRIS [5] at the ISIS, UK; LAM-80 [6] at the KENS, Japan; or MARS [7] at the SINQ, Switzerland.
Mamontov, Eugene [ORNL; Zamponi, Michaela M [ORNL; Hammons, Stephanie E [ORNL; Keener, Wylie S [ORNL; Hagen, Mark E [ORNL; Herwig, Kenneth W [ORNL
Beta -Backscatter Measurement of Thin-Gold Coatings.
National Technical Information Service (NTIS)
A beta-backscattering thickness gauge for measuring gold coatings in the 8,000 to 16,000 A thickness range on codeposited chromium and gold coatings on ceramic substrates is briefly described. (ERA citation 02:039807)
P. L. Blue
Simulation of coherent backscattering of light in nematic liquid crystals
Multiple scattering of light by the fluctuations of the director in a nematic liquid crystal (NLC) aligned by a magnetic field is considered. A peak of coherent backscattering is calculated by numerical simulation. Since the indicatrix of single scattering for a liquid crystal (LC) is known exactly, the calculations are carried out without any simplifying assumptions on the parameters of the liquid crystal. Multiple scattering is simulated as a random walk of photons in the medium. A peak of coherent backscattering in such a medium is very narrow; therefore, the so-called semianalytical method is applied. The parameters of the backscattering peak obtained by numerical simulation are compared with the available experimental data and with the results of analytical approximations. It turns out that the experimental data are in good agreement with the results of simulation. The results of numerical simulation adequately describe the anisotropy and the width of the backscattering peak.
Aksenova, E. V., E-mail: firstname.lastname@example.com; Kokorin, D. I., E-mail: email@example.com; Romanov, V. P., E-mail: firstname.lastname@example.com [St. Petersburg State University (Russian Federation)
Ocean Wave Slope Observations Using Radar Backscatter and Laser Altimeters
Combination of laser and radar aboard an aircraft is used to directly measure long gravity wave surface tilting simultaneously with nadir-viewing microwave backscatter from the sea surface. The presented dataset is exten- sive, encompassing varied wind conditions over coastal and open-ocean wave regimes. Laser-derived slope statistics and Ka-band (36 GHz) radar backscatter are detailed separately to document their respective variations
D. Vandemark; B. Chapron; J. Sun; G. H. Crescenti; H. C. Graber
Directional ultrasonic backscattering in polycrystals with elongated grains
NASA Astrophysics Data System (ADS)
An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated grains is obtained. The theory was applied to evaluation of experimental data in Ti alloy with duplex microstructure, which consists of micro-textured regions (MTR) and smaller crystallites. Experiment shows that for microstructure characterization there is significant advantage in using the directional ratios of backscattering coefficients instead their absolute values for data analysis.
Lobkis, O. I.; Yang, L.; Li, J.; Rokhlin, S. I.
A Backscattering Enhanced Microwave Canopy Scattering Model Based On MIMICS
NASA Astrophysics Data System (ADS)
For modeling microwave scattering of vegetated areas, several microwave canopy scattering models, based on the vectorized radiative transfer equation (VRT) that use different solving techniques, have been proposed in the past three decades. As an iterative solution of VRT at low orders, the Michigan Microwave Canopy Scattering Model (MIMICS) gives an analytical expression for calculating scattering as long as the volume scattering is not too strong. The most important usage of such models is to predict scattering in the backscattering direction. Unfortunately, the simplified assumption of MIMICS is that the scattering between the ground and trunk layers only includes the specular reflection. As a result, MIMICS includes a dominant coherent term which vanishes in the backscattering direction because this term contains a delta function factor of zero in this direction. This assumption needs reconsideration for accurately calculating the backscattering. In the framework of MIMICS, any incoherent terms that involve surface scattering factors must at least undergo surface scattering twice and volume scattering once. Therefore, these incoherent terms are usually very weak. On the other hand, due to the phenomenon of backscattering enhancement, the surface scattering in the backscattering direction is very strong compared to most other directions. Considering the facts discussed above, it is reasonable to add a surface backscattering term to the last equation of the boundary conditions of MIMICS. More terms appear in the final result including a backscattering coherent term which enhances the backscattering. The modified model is compared with the original MIMICS (version 1.0) using JPL/AIRSAR data from NASA Campaign Soil Moisture Experimental 2003 (SMEX03) and Washita92. Significant improvement is observed.
Shen, X.; Hong, Y.; Qin, Q.; Chen, S.; Grout, T.
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
[Simulation of backscattering coefficients of inland waters].
When we simulated backscattering coefficients (b(bp)) using quasi-analytical algorithm and optical closure theory, it was found that the position of reference wavelength (lambda(0)) had great impact on final results. In order to identify influence factors of the optimum lambda(0), datasets of Lake Taihu, Lake Chaohu and Lake Dianchi were used. After simulating of b(bp), the relationship between optimum lambda(0) and associated water quality parameters were analyzed. Meanwhile, power functions were utilized to model b(bp) spectra, and spectral slope parameters of Lake Taihu, Lake Chaohu and Lake Dianchi were 2.643 +/- 0.317, 2.719 +/- 0.242, 1.638 +/- 0.534, respectively. The results indicate that: (1) When the whole lakes are taken as objects of study, the lambda(0) should be changed to longer wavelength with the increasing of total suspended particle matter concentration (c(SPM)), suspended organic particle matter concentration (c(SPOM)) and chlorophyll a concentration (c(CHL)), the optimum location of lambda(0) of Lake Taihu is 695 nm, Lake Chaohu is 720 nm and Lake Dianchi is 730 nm; (2) When the samples in lakes are taken as objects of study, the influence factors are different due to the complexity of optical properties of inland waters. But it is to be noted that, c(SPM) is a key factor in common. Besides, the regularity mentioned above should be weakened with high c(CHL). (3) The relationship between b(bp) and c(SPM) is much stronger in the waters with suspended particles dominated by inorganic particles, in Lake Taihu, for example, relationship between these two variables is strong with R2 = 0.852. PMID:22165215
Zhang, Hong; Li, Yun-Mei; Huang, Jia-Zhu; Liu, Zhong-Hua; Xu, Yi-Fan; Xu, Xin; Guo, Yu-Long; Tan, Jing
A new iterative process for accurate analysis of displaced atoms from channeling Rutherford backscattering spectrometry
We have developed an iterative process to distinguish the yield contribution of the channeled He ions directly backscattered by displaced atoms and the yield contribution from the dechanneled He ions backscattered by lattice displaced atoms in channeling Rutherford backscattering spectrometry (RBS). The iterative process is able to accurately calculate the dechanneled fraction, the directly backscattered fraction and the dechanneling cross-section.
Lin Shao; Y. Q. Wang; M. Nastasi
Bomb Detection Using Backscattered X-Rays
Bomb Detection Using Backscattered X-rays* Currently the most common method to determine the contents of a package suspected of containing an explosive device is to use transmission radiography. This technique requires that an x-ray source and film be placed on opposite sides of the package. This poses a problem if the pachge is placed so that only one side is accessible, such as against a wall. There is also a threat to persomel and property since exTlosive devices may be "booby trapped." We have developed a method to x-ray a paclage using backscattered x-rays. This procedure eliminates the use of film behind the target. All of the detection is done from the same side as the source. When an object is subjected to x-rays, some of them iare scattered back towards the source. The backscattenng of x-rays is propordoml to the atomic number (Z) of the material raised to the 4.1 power. This 24"' dependence allows us to easily distinguish between explosives, wires, timer, batteries, and other bomb components. Using transmission radiography-to image the contents of an unknown package poses some undesirable risks. The object must have an x-ray film placed on the side opposite the x-ray source; this cannot be done without moving the package if it has been placed firmly against a wall or pillar. Therefore it would be extremely usefid to be able to image the contents of a package from only one side, without ever having to disturb the package itself. where E is the energy of the incoming x-ray. The volume of x-rays absorbed is important because it is, of course, directly correlated to the intensity of x-mys that will be scattered. Most of the x-rays that scatter will do so in a genemlly forward direction; however, a small percentage do scatter in a backward direction. Figure 1 shows a diagram of the various fates of x-rays directed into an object. The package that was examined in this ex~enment was an attache case made of pressed fiberboardwith a vinyl covering. It was approxirmtely 36 cm wide by 51 cm long by 13 cm deep. The case was placed on an aluminum sheet under the x-ray source. Because of the laborato~ setup, the attache case was rastered in the y-coordinate direction, while the x-ray source mstered in the x-coordinate direction. However, for field use, the x-ray source would of course raster in both the x- and y-coordinate directions, while the object under interrogation would remain stationary and undisturbed. A mobile system for use by law enforcement agencies or bomb disposal squads needs to be portable and somewhat durable. A 300 kV x-ray source should be sufficient for the task requirements and can be mounted on a mobile system. A robotic carriage could be used to transport the x-ray source and the CCD camera to the proximity of the suspect package. The controlling and data analyzing elements of the system' could then be maintained at a &tie distance from the possible explosive. F@re 8 shows a diagram of a conceptual design of a possible system for this type of use. The use of backscattered x-rays for interrogation of packages that may contain explosive devices has been shown to be feasible inthelaboratory. Usinga 150kVx-ray source anddetectors consisting of plastic scintillating material, all bomb components including the wiring were detectable. However, at this time the process requires more time than is desirable for the situations in which it will most likely be needed. Further development of the technology using CCD cameras, rather than the plastic stint illator detectors, shows promise of leading to a much faster system, as well as one with better resolution. Mounting the x- ray source and the CCD camera on a robotic vehicle while keeping the controlling and analyzing components and the opemting personnel a safe distance away from the suspect package will allow such a package to be examined at low risk to human life.
Jacobs, J.; Lockwood, G.; Selph, M; Shope, S.; Wehlburg, J.
Nonlinear diffractive optical elements.
We propose diffractive optical elements with a spatially-varying nonlinear refractive index. Such a component acts as a diffractive optical element whose properties depend on the intensity of the incoming beam. We present a method for designing such elements, and as specific examples we study three types of nonlinear diffractive optical elements: Nonlinear Fresnel Zone Plates, Two-foci Nonlinear Fresnel Zone Plate, and Fresnel Zone Plate to Grating interpolator. PMID:19547443
Manela, Ofer; Segev, Mordechai
Orientation mapping of nanostructured materials using transmission Kikuchi diffraction in the scanning electron microscope.
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
Robustness of Cantor diffractals.
Diffractals are electromagnetic waves diffracted by a fractal aperture. In an earlier paper, we reported an important property of Cantor diffractals, that of redundancy [R. Verma et. al., Opt. Express 20, 8250 (2012)]. In this paper, we report another important property, that of robustness. The question we address is: How much disorder in the Cantor grating can be accommodated by diffractals to continue to yield faithfully its fractal dimension and generator? This answer is of consequence in a number of physical problems involving fractal architecture. PMID:23571887
Verma, Rupesh; Sharma, Manoj Kumar; Banerjee, Varsha; Senthilkumaran, Paramasivam
Coherent Backscattering in Los Albedo Media
NASA Astrophysics Data System (ADS)
The opposition effect [1] observed in phase curves of materials in the lab and on planetary surfaces is attributed to two processes: 'shadow hiding opposition effect' (SHOE) and 'coherent backscattering opposition effect' (CBOE) [2,3,4]. The relative contributions of SHOE and CBOE are studied by measuring reflectance phase curves in circularly polarized light. If single scattering predominates, the circular polarization ratio (CPR) decreases with decreasing phase angle. If multiple scattering predominates, the CPR strongly increases. We observed this increase in CPR in highly reflective media [5,6,7]. In low reflectance media most of the returned signal is singly scattered and CPR is not expected to sharply increase. We have found that most such materials indeed exhibit only a slight CPR increase. However, lunar soils show a strong CPR increase [8]. Recently we encountered another interesting counter example in Boron Carbide-a material with albedo even lower than the Moon's. We find a significant CPR increase, a result inconsistent with the conventional interpretation of CBOE [8]. This suggests that albedo alone is not the principal regulator of CBOE. This CBOE may be due to multiple scattering within individual particles [10]. Unusual particle shapes may facilitate this process. Understanding this behavior contributes to the development of models that can retrieve textural properties from remote sensing data. Work performed at JPL/PITT under NASA PG&G grants. 1.Geherels, T. Astrophys. J, 123, 331-338, 1956. 2. Hapke, B. Icarus, 67, 246-280, 1986. 3. Shkuratov, Yu. SA-A.J., 27, 581-583, 1983. 4. Hapke, B. Icarus, 88, 407-417, 1990. 5. Nelson, R., et al. Icarus 131, 223-230, 1998. 6. Nelson, R., et al Icarus, 147, 545-558, 2000. 7. Nelson, R., et al. Planet. Space Sci, 2002. 8. Hapke B. et al. Science, 260, 509-511. 9. Mishchenko, M.I. Earth, Moon and Planets, 58, 127-144, 1992. 10. Hapke, B. Icarus, 157, 534-537, 2002
Nelson, R. M.; Hapke, B. W.; Hale, A. S.; Smythe, W. D.; Piatek, J.
Experimental Program to Elucidate and Control Stimulated Brillouin and Raman Backscattering in Long-Scale Plasmas
Laser-plasma instability is a serious concern for indirect-drive inertial confinement fusion (ICF), where laser beams illuminate the interior of a cavity (called a hohlraum) to produce X-rays to drive the implosion of a fusion capsule. Stimulated Raman and Brillouin backscattering (SRS and SBS) could result in unacceptably high laser reflectivities. Unfortunately, it is impossible at present to fully simulate these processes realistically. The authors experimental program aims to understand these instabilities by pursuing a dual strategy. (1) They use a gas-filled hohlraum design, which best approaches ignition-hohlraum conditions, on the Nova laser to identify important non linear trends. (2) They are shifting towards more fundamental experiments with a nearly diffraction-limited interaction laser beam illuminating extremely well characterized plasmas on the Trident laser facility at Los Alamos to probe the relevant fundamental processes.
Fernandez, J.C.; Cobble, J.A.; Montgomery, D.S.; Wilke, M.D.
High-Resolution Thermal Expansion Measurements of Single-Crystal Sapphire for Application as X-Ray Backscattering Monochromator
NASA Astrophysics Data System (ADS)
We report measurements of the thermal expansion of high-purity single crystal sapphire along the a and c directions. The data were acquired using a thermal expansion cell that is constructed of fused silica with a relative resolution of approximately 3x10-9. Comparison will be made to existing literature values determined from dilatometry and high-resolution x-ray diffraction. This project's main goal is the use of sapphire as x-ray backscattering monochromator for phonon spectroscopy using nuclear inelastic scattering. Tuning of the monochromator is done by varying the sapphire temperature, and the new thermal expansion values will improve the energy calibration.
Neumeier, John J.; Sergeev, I.; Bessas, D.; Hermann, R. P.
Sheared lherzolite xenoliths revisited
The microstructures of sheared lherzolite xenoliths from South African kimberlites are investigated using new microstructural analysis techniques and new rheological data. By applying electron backscatter diffraction (EBSD) methods and the M-index technique for quantifying the strength of lattice preferred orientation (LPO), it is demonstrated that olivine and orthopyroxene, after an initial stage of dynamic recrystallization, deformed by different mechanisms: olivine
Philip Skemer; Shun-ichiro Karato
Stress, texture and electromigration in damascene copper interconnects
Recently Al was replaced by Cu as an interconnecting material. The primary objective of the present research was to investigate the mechanism of texture and microstructure evolution and to study its influence on electromigration in damascene Cu interconnects. For this purpose electromigration experiments were performed on the Cu interconnects in vacuum in the SEM. The in-situ electron back-scatter diffraction (EBSD)
Kabir Mirpuri
Calcite epitaxy on Au and Ag (1 1 1)
Crystallization control is an intensely studied field. This study concerns synthesis of epitaxial calcite on Au and Ag substrate without the use of any template. The crystals were analyzed in situ by micro-Raman spectroscopy and ex situ by Scanning Electron Microscopy (SEM) and Electron Backscattering Diffraction (EBSD). Undersaturated solution containing only calcium and hydrogen carbonate is used. Electrochemically induced dissolved
Hassiba Teghidet; Marie Claude Bernard; Stephan Borensztajn; Lila Chaal; Suzanne Joiret; Boualem Saidani
Evolution of deformation texture in Al\\/Al¢Mg\\/Al composite sheets during cold-roll cladding
Al\\/Al¢Mg\\/Al composite sheets were fabricated by roll cladding to investigate the evolution of deformation texture through the thickness direction. Electron backscatter diffraction (EBSD) was used to analyze the heterogeneity of deformation texture in each component layer of the composite sheets. Finite element analysis (FEA) was conducted to simulate the deformation history in each component layer during roll cladding. The deformation
Eun-Young Kim; JaeHyung Cho; Hyoung-Wook Kim; Shi-Hoon Choi
The {sigma} phase formation in annealed UNS S31803 duplex stainless steel: Texture aspects
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: firstname.lastname@example.com; 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)
Modeling uniaxial tensile deformation of polycrystalline Al using CPFEM
The crystal plasticity finite element modeling (CPFEM) is realized in commercial finite element code ABAQUS with UMAT subroutine on the basis of the crystal plasticity theory of rate dependent polycrystal constitutive relations in the mesoscopic scale. The initial orientations obtained by electron backscatter diffraction (EBSD) are directly input into the CPFEM to simulate the mechanical response of polycrystalline 1050 pure
Huachun Pi; Jingtao Han; Chuanguo Zhang; A. Kiet Tieu; Zhengyi Jiang
Columnar to equiaxed transition of eutectic in hypoeutectic aluminium¢silicon alloys
Directional solidification of unmodified and strontium modified binary, high-purity, aluminium¢7 wt% silicon and commercial A356 alloys has been carried out to investigate the mechanism of eutectic solidification. The microstructure of the eutectic growth interface was investigated with optical microscopy and Electron Backscattering Diffraction (EBSD). In the commercial alloys, the eutectic solidification interface extends in the growth direction and creates a
G. Heiberg; K. Nogita; A. K. Dahle; L. Arnberg
Modeling the Viscous to Plastic Transition in Mid-Ocean Ridge Gabbros: Implications for Crystallographic Preferred Orientation of Plagioclase and Seismic Anisotropy
Gabbroic rocks are a key component of our understanding of the physical properties (rheology, seismic velocities and anisotropy, ...) of the oceanic crust. We have established a database of over 50 samples of crystallographic preferred orientation (CPO) in gabbroic rocks from the oceanic crust using electron backscattered diffraction EBSD. The measured samples cover magmatic flow to high temperature plastic flow
B. Ildefonse; D. Mainprice
Diffraction grating lens array
NASA Astrophysics Data System (ADS)
We have proposed a new type of camera module with a thin structure and distance-detection capability. This camera module has a four-lens-array with diffraction gratings (one for blue, one for red, and two for green). The diffraction gratings on the mold are formed mechanically, and the plastic lens array is fabricated by injection molding. The two green images are compared to detect parallax, and parallax-corrected blue, red and green images are then composed to generate a color image. We have developed new design software and molding technologies for the grating lenses. The depth and period of blazed gratings and the shapes of aspheric lenses are optimized; and blue, red and two green aspheric lenses with gratings are molded as a single four-lens-array. The diffraction gratings on both surfaces of each lens act to improve field curvature and realize wide-angle imaging. However, blazed gratings sometimes cause unnecessary diffraction lights that impede the formation ofhigh-resolution images. We have developed a new method to measure necessary first-order diffraction lights and unnecessary diffraction lights separately. Use of this method allows the relationship between molding conditions and necessary/unnecessary diffraction lights to be shown. Unnecessary diffraction lights can be diminished by employing the optimal molding processes, allowing our grating lenses to be used for image capture.
Korenaga, Tsuguhiro; Ando, Takamasa; Moriguchi, Seiji; Takami, Fuminori; Takasu, Yoshifumi; Nishiwaki, Seiji; Suzuki, Masa-aki; Nagashima, Michiyoshi
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
Modeling of ultrasonic backscatter using ultrasonic radiative transfer theory
NASA Astrophysics Data System (ADS)
The scattering of elastic waves in polycrystalline media is primarily due to the elastic inhomogeneities present between grains. This scattering may be used to extract the microstructural parameters of the material such as grain size and grain texture. In particular, ultrasonic backscatter measurements have been especially useful for extracting microstructural information. From the theoretical perspective, derivations related to ultrasonic radiative transfer equations (URTE) govern the propagation of diffuse intensities and include all multiple scattering effects. In this presentation, a rigorous connection between the URTE theory and the backscatter experiments is discussed. The general URTE formulation is first reduced to the singly scattered problem. The backscattered ultrasonic flux is shown to be the main quantity of interest. The flux is obtained in terms of the relevant scattering parameters. Specific solutions are obtained for a specimen excited by a normally incident longitudinal wave. The backscatter model for a normally incidental longitudinal wave and its mode converted shear wave are discussed. The theoretical results are compared with numerical simulations based on Voronoi polycrystal finite-element calculations. Results are also compared with previous backscattering theories. Relevant applications for materials of common interest are also discussed. [Work supported by DOE.
Ghoshal, Goutam; Turner, Joseph A.
Anomalous Radar Backscatter from Some Regions on Titan
NASA Astrophysics Data System (ADS)
Radar backscattering from some regions on Titan's surface observed by the Cassini RADAR is enhanced beyond what can be explained by current models for solar system surfaces. In particular, based on the application of Kirchhoff's law of radiation, we find that the backscattering cross sections in Xanadu and some other hummocky radar-bright regions are too high in relation to their observed emissivities to be explained by random scattering from inhomogeneities in a low-loss subsurface, even when coherent backscattering (cf. Hapke, 1990) is allowed for. We argue the need for the presence of ordered backscattering structure on certain terrains on Titan's surface. The radar-bright channels that likely result from past liquid flows are a particular example, where we show that the presence of rounded river ice "rocksö could indeed act in a manner analogous with the retroreflective paint used on highway signs to produce such anomalous backscatter. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Janssen, Michael A.; Le Gall, A.
Modeling multi-frequency diurnal backscatter from a walnut orchard
NASA Technical Reports Server (NTRS)
The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.
Mcdonald, Kyle C.; Dobson, Myron C.; Ulaby, Fawwaz T.
Radial reflection diffraction tomography
A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.
Lehman, Sean K.
Radial Reflection diffraction tomorgraphy
A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.
Lehman, Sean K
Feasibility of bone assessment with ultrasonic backscatter signals in neonates.
The objective of this study was to assess the value of ultrasonic backscatter signals and the backscatter coefficient (BSC) in the analysis of bone status in neonates and to analyze the relationships between the BSC and gestational age, birth weight, length, head circumference and gender. A total of 122 neonates participated in the study, including 83 premature infants and 39 full-term infants. Their BSCs were measured by ultrasound after birth. The results revealed a significant correlation between the BSC and gestational age (R = 0.47, p < 0.001), birth weight (R = 0.47, p < 0.0001) and length at birth (R = 0.43, p < 0.001) at a frequency of 5.0 MHz. This study suggests that the use of ultrasonic backscattering and the BSC is feasible for assessment of the bone status of neonates. PMID:23932274
Zhang, Rong; Ta, Dean; Liu, Chengcheng; Chen, Chao
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
Coherent backscattering of electromagnetic waves in random media
NASA Astrophysics Data System (ADS)
The single and multiple scattering regimes of electromagnetic waves in a disordered system with fluctuating permittivity are studied by numerical simulations of Maxwell's equations. For an array of emitters and receivers in front of a medium with randomly varying dielectric constant, we calculate the backscattering matrix from the signal responses at all receiver points j to electromagnetic pulses generated at each emitter point i. We show that the statistical properties of the backscattering matrix are in agreement with the recent experimental results for ultrasonic waves (Aubry A. and Derode A., Phys. Rev. Lett., 102 (2009) 084301) and light (Popoff S. M. et al., Phys. Rev. Lett., 104 (2010) 100601). In the multiple scattering regime the singular value distribution of the backscattering matrix obeys the quarter-circle law.
Sheikhan, A.; Maass, P.; Rahimi Tabar, M. Reza
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
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.
Significant progress has been made toward solving the century-old problem of chromatic aberrations in diffractive optics. Our approach exploits modern materials and microfabrication technology and is very different from the purely diffractive strategy,'' which is commonly employed and which results in multiple diffractive elements separated by a finite distance. We have developed a Fresnel zone plate lens comprised of a serial stack of patterned minus-filters which allows broadband radiation to be focused (or imaged) without longitudinal or transverse chromatic aberrations. 7 refs., 4 figs.
Ceglio, N.M.; Hawryluk, A.M.; London, R.A.; Seppala, L.G. (Lawrence Livermore National Lab., CA (USA)); Gaines, D.P. (Brigham Young Univ., Provo, UT (USA))
Multilayer dielectric diffraction gratings
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)
Multilayer dielectric diffraction gratings
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.
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.
X-ray backscatter imaging for aerospace applications
Scatter x-ray imaging (SXI) is a real time, digital, x-ray backscatter imaging technique that allows radiographs to be taken from one side of an object. This x-ray backscatter imaging technique offers many advantages over conventional transmission radiography that include single-sided access and extremely low radiation fields compared to conventional open source industrial radiography. Examples of some applications include the detection of corrosion, foreign object debris, water intrusion, cracking, impact damage and leak detection in a variety of material such as aluminum, composites, honeycomb structures, and titanium.
Shedlock, Daniel [Nucsafe, Inc., 601 Oak Ridge Turnpike, Oak Ridge, TN 37830 (United States); Edwards, Talion [Boeing Research and Technology, 5775 Campus Parkway, Hazelwood, MO 63042 (United States); Toh, Chin [Boeing Research and Technology, 2201 Seal Beach Blvd, Seal Beach, CA 90740 (United States)
Carbon dioxide laser backscatter signatures from laboratory-generated dust
NASA Astrophysics Data System (ADS)
A dual CO2 laser system was used to measure aerosol backscatter spectral signatures from dust minerals (kaolin, illite, montmorillonite, colemanite, and limestone) as well as from a soil sample from Dugway Proving Ground, UT. Complex refractive indices measured from bulk samples of the materials, and particle size distributions measured with a cascade impactor, were used to compute theoretical backscatter spectra using Mie theory. The measured signatures agreed well with calculated signatures for most minerals and the soil sample. The experiment demonstrated the feasibility of detecting the compositional elements of dust using a CO2 laser-based system.
Walter, D. P.; Cooper, D. E.; van der Laan, J. E.; Murray, E. R.
Backscatter effects of surfaces composed of dry biological particles
NASA Astrophysics Data System (ADS)
We present the backscattering of particulate surfaces consisting of dry biological particles using two laboratory photopolarimeters that measure intensity and degree of linear polarization in a phase-angle range 0.2 60░. We measure scattering properties from three samples composed of dry biological particles, Bacillus subtilis var. niger (BG) spores and samples of fungi Aspergillus terreus and Sporisorium cruentum spores. We find that the surfaces display a prominent brightness opposition effect and significant negative polarization near backscattering angles. The brightness and polarimetric phase curves are different for B. subtilis and the fungi.
Ovcharenko, Andrey; Bondarenko, Sergey; Shkuratov, Yuriy; Scotto, Cathy; Merritt, Charles; Hart, Matthew; Eversole, Jay; Videen, Gorden
Target reflectance measurements for calibration of lidar atmospheric backscatter data
NASA Technical Reports Server (NTRS)
Wavelength and angular dependence of reflectances and depolarization in the 9-11 micron region are reported for four standard targets: flowers of sulfur, flame-sprayed aluminum, 20-grit sandblasted aluminum, and 400-grit silicon carbon sandpaper. Measurements are presented and compared using a CW CO2 grating-tunable laser in a laboratory backscatter apparatus, an integrating sphere, and a coherent pulsed TEA-CO2 lidar system operating in the 9-11 micron region. Reflectance theory related to the use of hard targets to calibrate lidar atmospheric backscatter data is discussed.
Kavaya, M. J.; Menzies, R. T.; Haner, D. A.; Oppenheim, U. P.; Flamant, P. H.
Robust diffraction correction method for high-frequency ultrasonic tissue characterization
NASA Astrophysics Data System (ADS)
The computation of quantitative ultrasonic parameters such as the attenuation or backscatter coefficient requires compensation for diffraction effects. In this work a simple and accurate diffraction correction method for skin characterization requiring only a single focal zone is developed. The advantage of this method is that the transducer need not be mechanically repositioned to collect data from several focal zones, thereby reducing the time of imaging and preventing motion artifacts. Data were first collected under controlled conditions from skin of volunteers using a high-frequency system (center frequency=33 MHz, BW=28 MHz) at 19 focal zones through axial translation. Using these data, mean backscatter power spectra were computed as a function of the distance between the transducer and the tissue, which then served as empirical diffraction correction curves for subsequent data. The method was demonstrated on patients patch-tested for contact dermatitis. The computed attenuation coefficient slope was significantly (p<0.05) lower at the affected site (0.13+/-0.02 dB/mm/MHz) compared to nearby normal skin (0.2+/-0.05 dB/mm/MHz). The mean backscatter level was also significantly lower at the affected site (6.7+/-2.1 in arbitrary units) compared to normal skin (11.3+/-3.2). These results show diffraction corrected ultrasonic parameters can differentiate normal from affected skin tissues.
Raju, Balasundar
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.
NASA Astrophysics Data System (ADS)
Some new experimental information is discussed, which supports the hypothesis that the Centauro events reported by cosmic ray experiments may indeed be produced diffractively as proposed by the author in 1986.
Goulianos, K.
National Technical Information Service (NTIS)
The report summarizes the need for concave diffraction gratings in ultraviolet, visible, and near infra-red spectroscopy, and provides a brief resume of the relative merits of ruled gratings and those generated using interference or 'holographic' techniqu...
M. C. Hutley
Gravitational diffraction radiation
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.
Cardoso, Vitor; Cavaglia, Marco; Pimenta, Mario [Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677-1848 (United States); Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677-1848 (United States); Departamento de Fisica, IST, Avenida Rovisco Pais, 1049-001 Lisbon (Portugal); LIP, Avenida Elias Garcia, 14-1, 1000-149 Lisbon (Portugal)
Fraunhofer Diffraction and Polarization.
ERIC Educational Resources Information Center
Describes an experiment for the intermediate undergraduate optics laboratory designed to illustrate simultaneously some aspects of the phenomena of diffraction; interference, coherence, apodization, the Fresnel-Arago law; as well as of the interrelations between these concepts. (HM)
Fortin, E.
Diffractive vector meson production
NASA Astrophysics Data System (ADS)
This is a brief introduction to diffractive vector meson production, both exclusive ?p?V and large momentum transfer ?p?VX processes. I overview the theoretical basis for the perturbative description and some recent developments.
Enberg, R.
Optical backscattering properties of the "clearest" natural waters
NASA Astrophysics Data System (ADS)
During the BIOSOPE field campaign October-December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over ~8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117░, ?t(117░), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2ū10-5, 5ū10-6, and 2ū10-6 m-1 sr-1, respectively. These values were approximately 6%, 3%, and 3% of the scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: - bbp distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; - Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; - accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1 + 0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and - closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: - The clearest waters sampled were found at depths between 300 and 350 m, from 23.5░ S, 118░ W to 26░ S, 114░ W, where total backscattering at 650 nm was not distinguishable from pure seawater; - Distributions of particulate backscattering bbp across the central gyre exhibited a broad particle peak centered ~100 m; - The particulate backscattering ratio typically ranged between 0.4% and 0.6% through the majority of the central gyre from the surface to ~210 m, indicative of "soft" water-filled particles with low bulk refractive index; and - bbp at 532 and 650 nm showed a distinct secondary deeper layer centered ~230 m that was absent in particulate attenuation cp data. The particulate backscattering ratio was significantly higher in this layer than in the rest of the water column, reaching 1.2% in some locations. This high relative backscattering, along with the pigment composition and ecological niche of this layer, appear to be consistent with the coccolithophorid F. profunda. Moreover, results were consistent with several expectations extrapolated from theory and previous work in oceanic and coastal regions, supporting the conclusion that particulate and total backscattering could be resolved in these extremely clear natural waters.
Twardowski, M. S.; Claustre, H.; Freeman, S. A.; Stramski, D.; Huot, Y.
Optical backscattering properties of the "clearest" natural waters
NASA Astrophysics Data System (ADS)
During the BIOSOPE field campaign October-December 2004, measurements of inherent optical properties from the surface to 500 m depth were made with a ship profiler at stations covering over 8000 km through the Southeast Pacific Ocean. Data from a ~3000 km section containing the very clearest waters in the central gyre are reported here. The total volume scattering function at 117░, ?t(117░), was measured with a WET Labs ECO-BB3 sensor at 462, 532, and 650 nm with estimated uncertainties of 2ū10-5, 5ū10-6, and 2ū10-6 m-1 sr-1, respectively. These values were approximately 6%, 3%, and 3% of the volume scattering by pure seawater at their respective wavelengths. From a methodological perspective, there were several results: - distributions were resolvable even though some of the values from the central gyre were an order of magnitude lower than the lowest previous measurements in the literature; - Direct in-situ measurements of instrument dark offsets were necessary to accurately resolve backscattering at these low levels; - accurate pure seawater backscattering values are critical in determining particulate backscattering coefficients in the open ocean (not only in these very clear waters); the pure water scattering values determined by Buiteveld et al. (1994) with a [1+0.3S/37] adjustment for salinity based on Morel (1974) appear to be the most accurate estimates, with aggregate accuracies as low as a few percent; and - closure was demonstrated with subsurface reflectance measurements reported by Morel et al. (2007) within instrument precisions, a useful factor in validating the backscattering measurements. This methodology enabled several observations with respect to the hydrography and the use of backscattering as a biogeochemical proxy: -The clearest waters sampled were found at depths between 300 and 350 m, from 23.5░ S, 118░ W to 26░ S, 114░ W, where total backscattering at 650 nm was not distinguishable from pure seawater; -Distributions of particulate backscattering bbp across the central gyre exhibited a broad particle peak centered ~100 m; -The particulate backscattering ratio typically ranged between 0.4% and 0.6% at 650 nm through the majority of the central gyre from the surface to ~210 m, indicative of "soft" water-filled particles with low bulk refractive index; and - bbp showed a distinct secondary deeper layer centered ~230 m that was absent in particulate attenuation cp data. The particulate backscattering ratio was significantly higher in this layer than in the rest of the water column, reaching 1.2% in some locations. This high relative backscattering, along with the pigment composition and ecological niche of this layer, appear to be consistent with the coccolithophorid Florisphaera profunda. Moreover, results were consistent with several expectations extrapolated from theory and previous work in oceanic and coastal regions, supporting the conclusion that particulate and total backscattering could be resolved in these extremely clear natural waters.
Twardowski, M. S.; Claustre, H.; Freeman, S. A.; Stramski, D.; Huot, Y.
NASA Astrophysics Data System (ADS)
The most recent H1 and ZEUS data for diffractive structure functions are analyzed under three different theoretical approaches. This includes the Pomeron Structure Function (PSF) framework, Bartels-Ellis-Kowalski-W³sthoff (BEKW) color dipole approach and the Golec-Biernat-W³sthoff (GBW) saturation model. The models are shown to successfully fit the set of combined data. Conceptual differences between the models are discussed and, as an example, the prediction for the longitudinal diffractive structure function is presented.
Sapeta, S.
Diffraction grating lens array
We have proposed a new type of camera module with a thin structure and distance-detection capability. This camera module has a four-lens-array with diffraction gratings (one for blue, one for red, and two for green). The diffraction gratings on the mold are formed mechanically, and the plastic lens array is fabricated by injection molding. The two green images are compared
Tsuguhiro Korenaga; Takamasa Ando; Seiji Moriguchi; Fuminori Takami; Yoshifumi Takasu; Seiji Nishiwaki; Masa-aki Suzuki; Michiyoshi Nagashima
Reflective diffraction grating
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)
Multiple Slit Diffraction Model
NSDL National Science Digital Library
The EJS Multiple Slit Diffraction model allows the user to simulate Fraunhofer diffraction through single or multiple slits. The user can modify the number of slits, the slit width, the slit separation and the wavelength of the incident light. The scale of the diffraction pattern can also be changed and a plot of the light intensity can be toggled on and off with a checkbox. A basic theoretical introduction to diffraction is included. The Multiple Slit Diffraction Model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ntnu_optics_MultipleSlitDiffraction.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Open Source Physics programs for quantum mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or EJS.
Hwang, Fu-Kwun
Coherent nonlinear backscattering by laser-plasma interactions
A theoretical analysis is carried out for the problem of coherent nonlinear backscattering of laser radiation by a high density plasma. A number of effects of direct interest to the DT-pellet fusion research are investigated. A simple physical description is introduced, which relies on a nonlinear potential formulation of the scattering equations. The simplicity and the unified nature of the
D. Anderson; H. Wilhelmsson
An overview of backscattered radio frequency identification system (RFID)
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
Theory and measurement of backscattering from RFID tags
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
Coherent backscattering of light by cold atoms: Theory meets experiment
Coherent backscattering (CBS) of quasi-resonant light by cold atoms presents some specific features due to the internal structure of the atomic scatterers. We present the first quantitative comparison between the experimentally observed CBS cones and Monte Carlo calculations which take into account the shape of the atomic cloud as well as the internal atomic structure.
G. Labeyrie; D. Delande; C. A. M³ller; C. Miniatura; R. Kaiser
Active backscattered optical polarimetric imaging of scattered targets
The imaging potential of efficient optical polarimetric techniques, for active imaging through scattering media has been studied. Specifically, the depolarization of backscattered polarized laser light, based on the Mueller-matrices formalism, has been investigated. The experimental results indicate clearly that, scattered photons from disperse media maintain a high degree of linear polarization (DOLP). As a result, image quality and target recognition
G. C. Giakos
Helicopter-borne measurements of radar backscatter from forests
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 Hyyppõ; Erkki Somersalo; Pekka Ahola; Martti Toikka; Jouni Pulliainen
Bathymetry and acoustic backscatter: Elwha River Delta, Washington
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.
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 clamsŚboth 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
Simulation of Neutron Backscattering applied to organic material detection
The Neutron Backscattering technique is tested when performing the task of localizing hydrogenated explosives hidden in soil. Detector system, landmine, soil and neutron source are simulated with Geant4 in order to obtain the number of neutrons detected when several parameters like mine composition, relative position mine-source and soil moisture are varied.0.
Forero, N. C.; Cruz, A. H.; Cristancho, F. [Departamento de Fisica, Universidad Nacional de Colombia, Bogota (Colombia); Centro Internacional de Fisica, Apartado Aereo 4948, Bogota (Colombia)
Inversion of radar backscatter from millimeter wave smoke
This paper describes the results of an analysis of radar backscatter and attenuation data collected during field trials of the MMW Module of the XM56 Large Area Screening Generator. The trials were conducted by Edgewood Research Development and Engineering Center personnel at Dugway Proving Ground in 1989 and 1990, and at Eglin AFB in 1992. The purpose of this analysis
Benjamin Perry; D. J. Hale
Spectrum of coherently backscattered light from two atoms
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 as well as negative - or exhibits dispersive character. These distinctive features are explained by reciprocity arguments and dressed-state two-photon scattering amplitudes.
Shatokhin, Vyacheslav [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Strasse 38, 01187 Dresden (Germany); B. I. Stepanov Institute of Physics, National Academy of Sciences, Nezavisimosti Avenue 68, 220072 Minsk (Belarus); Wellens, Thomas [Institut fuer Theoretische Physik, Universitaet Erlangen-Nuernberg, Staudstrasse 7, 91058 Erlangen (Germany); Gremaud, Benoit [Laboratoire Kastler Brossel, Universite Pierre et Marie Curie, 4, place Jussieu, 75252 Paris Cedex 05 (France); Buchleitner, Andreas [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Strasse 38, 01187 Dresden (Germany)
Anisotropy of attenuation and backscatter in cancellous bone
Although bone sonometry is useful in the diagnosis of osteoporosis, the interactions between ultrasound and bone are not well understood yet. In order to investigate these processes, ultrasonic attenuation and backscatter in two orientations were measured in 43 human calcaneal specimens in vitro. In the mediolateral orientation, the ultrasound propagation direction is approximately perpendicular to the trabecular axes. In the
Keith A. Wear
Construction of a high resolution crystal backscattering spectrometer HERMES I.
National Technical Information Service (NTIS)
There is a need in the United States for a state-of-the-art, cold-neutron, crystal backscattering spectrometer (CBS) designed to investigate the structure and dynamics of condensed matter systems by the simultaneous utilization of long wavelength elastic ...
J. Z. Larese
Brillouin backscatter model in LASNEX: Improvements and additions
In the 1978 Annual Report, a stimulated Brillouin scatter (SBS) model for LASNEX was described. Many improvements and additions were made in 1979 in order to model the Brillouin backscatter in underdense plasmas more accurately. The density dependence of the model was changed and the effects of inhomogeneous media were included. A self consistent calculation of the hot ion contribution
J. Harte; K. Estabrook
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.
Monte Carlo simulations of coaxial backscattered electrons in SEM
We simulate the trajectories of backscattered electrons within a SEM of particular detection geometry which is adapted to topographic contrast attenuation and Z atomic number contrast enhancement. The calculations are performed choosing the different experimentally possible conditions as regards the primary electron energy, the detector aperture angle and the energy window of the detected electrons. From such simulations, it is
N. Rosenberg; C. Z. Jiang; P. Morin
Discrimination of UXO in soil using broadband polarimetric GPR backscatter
Polarimetric analysis of ground penetrating radar (GPR) backscatter offers a new means of discriminating subsurface metallic target shapes from one another. Such discrimination is urgently needed to distinguish buried unexploded ordnance (UXO) from other subsurface objects. To illuminate the underlying phenomenology of scattering from objects enveloped in soil, three-dimensional (3D) simulations are performed over a broad frequency band, characteristic of
Kevin O'Neill
Modelling of Rayleigh backscattering in plastic optical fiber
The Rayleigh scattering coefficient within plastic optical fiber (POF), which is also called turbidity, has been investigated and parameters affecting the level of turbidity have been located and discussed. The Rayleigh attenuation model has been built on turbidity and has been verified by comparing with published data. Disparities between the model and published data have been discussed. The Rayleigh backscattering
Cheng Gao; Gerald Farrell
Effect of the stimulated Brillouin backscattering on selffocusing threshold
In many physical problems stimulated Brillouin scattering (SBS) and selffocusing are manifested simultaneously. We consider effect of the stimulated Brillouin backscattering (SBS) on self-focusing of laser radiation in plasmas. It was found that the self-focusing may be supressed substantionally by the SBS effect.
Rubenchik, A.M. [Lawrence Livermore National Lab., CA (United States); Shapiro, E.G.; Turitsyn, S.K. [AN SSSR, Novosibirsk (Russian Federation). Inst. Avtomatiki i Ehlektrometrii
Comparison between EISCAT UHF and VHF backscattering cross section
We present a comparison between the backscattering cross sections at 224 and 933 MHz measured with European Incoherent Scatter (EISCAT) radars during the passage of a discrete arc. It shows a difference of 2 orders of magnitude which cannot simply be explained by normal thermal ionospheric density fluctuations. We claim that the observed difference in the scattering cross sections is
B. Cabrit; H. Opgenoorth; W. Kofman
A simple backscattering microscope for fast tracking of biological molecules
Recent developments in techniques for observing single molecules under light microscopes have helped reveal the mechanisms by which molecular machines work. A wide range of markers can be used to detect molecules, from single fluorophores to micron sized markers, depending on the research interest. Here, we present a new and simple objective-type backscattering microscope to track gold nanoparticles with nanometer
Yoshiyuki Sowa; Bradley C. Steel; Richard M. Berry
Inhomogeneus broadening parameters in Thomson-backscattering-based sources.
National Technical Information Service (NTIS)
The effect of electron and laser beam quality on Thomson backscattering of an intense laser beam, recently proposed as a means of obtaining a compact, tunable high-brightness x-ray source, is analyzed. In full analogy with magnetic undulator-based sources...
G. Dattoli A. Torre
Analytical solution for depth scale calculations in Rutherford backscattering spectrometry
An analytic approximation is presented that allows a straightforward calculation of impurity concentration depth profiles from a measured Rutherford backscattering spectrum. The depth scale calculations consider energy-dependent stopping power data. Calculation of the concentration assumes Rutherford cross sections including electron screening effects. The solution for the depth scale has been verified to be within 2% of the exact numerical solution
D. Shakhvorostov; W. N. Lennard; P. R. Norton
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.
Statistical moments of backscattered ultrasound in porous fiber reinforced composites
Statistical moments are important tools for understanding wave propagation in random media and are applied here to backscatter measurements in porous, fiber-reinforced polyimide composites. High temperature resins, such as PMR-15, used in load critical components are much more prone to void production than traditional epoxies. Porosity was induced in thin laminates by cure cycle perturbations and quantified destructively as to
Daniel Grolemund; Chen S. Tsai
Diffraction light analysis method for a diffraction grating imaging lens.
We have developed a new method to analyze the amount and distribution of diffraction light for a diffraction grating lens. We have found that diffraction light includes each-order diffraction light and striped diffraction light. In this paper, we describe characteristics of striped diffraction light and suggest a way to analyze diffraction light. Our analysis method, which considers the structure of diffraction grating steps, can simulate the aberrations of an optical system, each-order diffraction light, and striped diffraction light simultaneously with high accuracy. A comparison between the simulation and experimental results is presented, and we also show how our analysis method can be used to optimize a diffraction grating lens with low flare light. PMID:24787427
Ando, Takamasa; Korenaga, Tsuguhiro; Suzuki, Masa-Aki; Tanida, Jun
Backscatter Analysis of Saturn's Icy Moons with Cassini RADAR
NASA Astrophysics Data System (ADS)
The typical Saturn icy satellite RADAR observation occurs at large distances, usually about 100,000 km, but sometimes as far as 400,000 km. Ostro et al. (Icarus 2010) have reported 2 cm-wavelength radar albedo estimates and diffuse scattering parameters for 73 radar tracks acquired through April 2008 across eight of Saturn's moons. We reprocess this data, together with more recently acquired data (bringing the total to more than 91 tracks), using an alternative processing approach, where we project the weighted received power onto the surface rather than model the power spectral shape. This allows us to create an extensive set of consistently processed measurements that we can use to understand the distribution of 2 cm-wavelength scattering characteristics across each moon's surface, as well as between the moons. We focus on data acquired during several close targeted flybys occurring at distances smaller than 45,000 km. The targeted flyby data enable us to carefully measure the backscatter response for regions on Rhea, Iapetus, and Enceladus. We model the backscatter response with a diffuse cosine power law to estimate the backscatter parameters A and N, where A is a measure of the reflection strength and N is a measure of the directivity of the backscatter power pattern. Isotropic surfaces will have N=1, whereas Lambertian surfaces have N=2. Our close flyby measurements span the range from A=0.41 for Iapetus' dark leading hemisphere to A=3.51 for Enceladus' bright trailing hemisphere, representing some of the darkest and the brightest surfaces in the Saturnian system. The measured N values reveal that Iapetus appears more Lambertian (N=1.81) and Enceladus looks more isotropic (1.23). The Rhea measurements are in between the two extremes, but are closer to the bright end of the spectrum (A=2.14, N=1.35). The Iapetus observation exhibits a small quasispecular rise at angles less than 20 degrees, a backscatter response similar to those measured for features on Titan. We fit a Hagfors and an exponential quasispecular model to the low-angle backscatter, and the results imply a low effective dielectric constant, possibly indicative of porous solid hydrocarbons or porous carbon dioxide ice, and moderate large-scale (>>2.2 cm) facet slopes. This is the first detection of a quasispecular component on an icy moon other than Titan, indicating the presence (albeit small) of a surface scattering mechanism in addition to the more prominent diffuse volume scattering mechanism that tends to dominate the backscatter of icy surfaces. We also form low resolution real aperture backscatter images of Enceladus, Rhea, and Iapetus and compare these to co-located high resolution synthetic aperture backscatter images. We analyze the resolution effects on the appearance of the backscatter responses.
Wye, L.; Zebker, H. A.; Cassini Radar Team
Practical Implications of Pole Series Convergence and the Early-time in Transient Backscatter.
National Technical Information Service (NTIS)
Here we consider the convergence of the singularity expansion method (SEM) pole series representation of the transient backscatter in terms of the stability in the estimated poles from the time domain response. Using a numerically simulated backscattered ...
S. K. Hong T. D. Andreadis W. A. Davis W. S. Wall
Measurement of Multiple Scattering Effects with a Polarization Raman Elastic-Backscatter Lidar.
National Technical Information Service (NTIS)
A new method for the determination of multiple scattering effects is described. A polarization Raman elastic backscatter lidar is used, which allows the measurement of the depolarization of both the elastically backscattered light and the light Raman scat...
U. Wandinger A. Ansmann C. Weitkamp W. Michaelis
Multipath analysis diffraction calculations
NASA Technical Reports Server (NTRS)
This report describes extensions of the Kirchhoff diffraction equation to higher edge terms and discusses their suitability to model diffraction multipath effects of a small satellite structure. When receiving signals, at a satellite, from the Global Positioning System (GPS), reflected signals from the satellite structure result in multipath errors in the determination of the satellite position. Multipath error can be caused by diffraction of the reflected signals and a method of calculating this diffraction is required when using a facet model of the satellite. Several aspects of the Kirchhoff equation are discussed and numerical examples, in the near and far fields, are shown. The vector form of the extended Kirchhoff equation, by adding the Larmor-Tedone and Kottler edge terms, is given as a mathematical model in an appendix. The Kirchhoff equation was investigated as being easily implemented and of good accuracy in the basic form, especially in phase determination. The basic Kirchhoff can be extended for higher accuracy if desired. A brief discussion of the method of moments and the geometric theory of diffraction is included, but seems to offer no clear advantage in implementation over the Kirchhoff for facet models.
Statham, Richard B.
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.
Benchmarking EGSnrc in the kilovoltage energy range against experimental measurements of charged particle backscatter coefficients
This study benchmarks the EGSnrc Monte Carlo code in the energy range of interest to kilovoltage medical physics applications (5-140 keV) against experimental measurements of charged particle backscatter coefficients. The benchmark consists of experimental data from 20 different published experiments (1954-2007) covering 35 different elements (4 <= Z <= 92), electron and positron backscatter, normal and oblique incidence, and backscatter
E. S. M. Ali; D. W. O. Rogers
Benchmarking EGSnrc in the kilovoltage energy range against experimental measurements of charged particle backscatter coefficients
This study benchmarks the EGSnrc Monte Carlo code in the energy range of interest to kilovoltage medical physics applications (5¢140 keV) against experimental measurements of charged particle backscatter coefficients. The benchmark consists of experimental data from 20 different published experiments (1954¢2007) covering 35 different elements (4 ? Z ? 92), electron and positron backscatter, normal and oblique incidence, and backscatter
E S M Ali; D W O Rogers
Interference of Backscatter from Two Droplets in a Focused Continuous Wave CO2 Doppler Lidar Beam
NASA Technical Reports Server (NTRS)
Superposition of backscatter from two silicone oil droplets in a lidar beam was observed as an interference pattern on a single backscatter pulse with a distinct periodicity of 2 & #61552; also agreeing extremely well with theory. Slightly differing droplet speeds caused phase differences in backscatter, resulting in the interference pattern.
Jarzembski, Maurice A.; Srivastava, Vandana
Texture analysis of melt-textured YBCO superconductors
NASA Astrophysics Data System (ADS)
We compare the results of an X-ray based pole figure texture analysis with the local texture analysis by means of electron-backscatter diffraction (EBSD) analysis. As samples, we employ two different melt-textured YBCO samples; one fully processed and one without oxygen treatment. To enable the direct comparison of the two techniques, we employ the [1 0 3] pole figures. We find a clear coincidence between the results obtained by the two measurement techniques on our samples, however, the EBSD results are much more detailed, yielding the local grain orientation distribution and quantitative results of the grain or subgrain misorientation angles. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis. The surface preparation procedure is essential to enable the automated EBSD mapping as high image quality Kikuchi patterns are required. The polishing procedures are discussed in detail.
Koblischka-Veneva, A.; Koblischka, M. R.; Simon, P.; Ogasawara, K.; Murakami, M.
MicroDiffraction in the Scanning Electron Microscope (SEM)
The identification of crystallographic phases in the scanning electron microscope (SEM) has been limited by the lack of a simple way to obtain electron diffraction data of an unknown while observing the micro structure of the specimen. With the development of Charge Coupled Device (CCD) based detectors, backscattered electron Kikuchi patterns (BEKP), alternately referred to as electron backscattered diffraction patterns (EBSP), can be easily collected. Previously, BEKP has been limited to crystallographic orientation studies due to the poor pattern quality collected with video rate detector systems. With CCD detectors, a typical BEKP can now be acquired from a micron or sub-micron-sized crystal using an exposure time of 1-10 seconds with an accelerating voltage of 10-40 kV and a beam current as low as 0.1 nA. Crystallographic phase analysis using BEKP is unique in that the properly equipped SEM permits high magnification images, BEKP`s, and elemental information to be collected from bulk specimens. BEKP in the SEM has numerous advantages over other electron microscopy crystallographic techniques. The large angular view ( 70 degrees) provided by BEKP and the lack of difficult specimen preparation are distinct advantages of the technique. No sample preparation beyond what is commonly used for SEM specimens is required for BEKP.
Goehner, R.P.; Michael, J.R.; Schlienger, M.E.
Advances in direct and diffraction methods for surface structural determination
NASA Astrophysics Data System (ADS)
I describe recent advances in low-energy electron diffraction holography and photoelectron diffraction holography. These are direct methods for determining the surface structure. I show that for LEED and PD spectra taken in an energy and angular mesh, the relative phase between the reference wave and the scattered wave has a known geometric form if the spectra are always taken from within a small angular cone in the near backscattering direction. By using data in the backscattering small cone at each direction of interest, a simple algorithm is developed to invert the spectra and extract object atomic positions with no input of calculated dynamic factors. I also describe the use of a convergent iterative method of PD and LEED. The computation time of this method scales as N2, where N is the dimension of the propagator matrix, rather than N3 as in conventional Gaussian substitutional methods. Both the Rehr-Albers separable-propagator cluster approach and the slab-type non-separable approach can be cast in the new iterative form. With substantial savings in computational time and no loss in numerical accuracy, this method is very useful in applications of multiple scattering theory, particularly for systems involving either very large unit cells (>300 atoms) or where no long-range order is present.
Tong, S. Y.
I discuss events in high energy hadron collisions that contain a hard scattering, in the sense that very heavy quarks or high P/sub T/ jets are produced, yet are diffractive, in the sense that one of the incident hadrons is scattered with only a small energy loss. 8 refs.
Berger, E.L.; Collins, J.C.; Soper, D.E.; Sterman, G.
Diffraction Constants of Transducers.
National Technical Information Service (NTIS)
The concept of a transducer diffraction constant as the ratio of the blocked diaphragm pressure to the incident free-field pressure is examined for meaning, definition, and application in the general case. The concept is extended to a transmitting transdu...
R. J. Bobber
NSDL National Science Digital Library
A series of laboratory activities on x-ray diffraction physics using the Teltron Tel-X-Ometer System. Detailed explanations on the production and delivery of the beam is included, as well as a very complete safety protocol for conducting the experiments.
Langan, Shawn
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)
NSDL National Science Digital Library
This applet simulates Fresnel diffraction patterns from monochromatic light through various apertures, including circles, half-plane, slit, double slit, corner, cross and more. The aperture scale is adjustable. The page also includes source code and links to other Fresnel applets/pages.
Falstad, Paul
The electric field diffracted by a strip caused by an incident cylindrical wave with E parallel to the edge, at various angles of incidence, is measured in a parallel plane medium. The field is compared with that computed from geometrical optics currents and with the addition of equivalent line currents at the edges. The edge \\
R. Plonsey
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.
Casta±eda, R.; Betancur, R.; Herrera, J.; Carrasquilla, J.
Bathymetry and Acoustic Backscatter: Northern Santa Barbara Channel, Southern California
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
Backscattering observation of radiation damage in optical fibers
NASA Astrophysics Data System (ADS)
The backscattering technique proposed by Barnoski et al. (1976) is applied to the problem of assessing the damage induced by nuclear radiation. The technique is shown to offer a number of advantages. For one, it makes possible real-time measurements from a single end. The fiber need not be removed from the place where the irradiation occurs; the measurement thus does not interfere with the usual fiber operation. In addition, it is possible to find the sections of the fiber where the major faults are located, and the presence of fractures can be seen. Preliminary measurements establishing the feasibility of the method, as well as some of its limitations, are presented. The possibility of using the backscattering method as a probe in radiation environments, such a nuclear plants, to find 'hotter' points in real time is considered.
Menaglia, F.; Piccari, L.; Bertolotti, M.; Serra, A.; Scheggi, A. M.
Stimulated brillouin backscatter of a short-pulse laser
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.
Effects of vegetation canopy on the radar backscattering coefficient
NASA Technical Reports Server (NTRS)
Airborne L- and C-band scatterometer data, taken over both vegetation-covered and bare fields, were systematically analyzed and theoretically reproduced, using a recently developed model for calculating radar backscattering coefficients of rough soil surfaces. The results show that the model can reproduce the observed angular variations of radar backscattering coefficient quite well via a least-squares fit method. Best fits to the data provide estimates of the statistical properties of the surface roughness, which is characterized by two parameters: the standard deviation of surface height, and the surface correlation length. In addition, the processes of vegetation attenuation and volume scattering require two canopy parameters, the canopy optical thickness and a volume scattering factor. Canopy parameter values for individual vegetation types, including alfalfa, milo and corn, were also determined from the best-fit results. The uncertainties in the scatterometer data were also explored.
Mo, T.; Blanchard, B. J.; Schmugge, T. J.
Z dependence of thick-target. beta. -ray backscattering
Variation of ..beta..-ray backscattering with the atomic number of target material has been studied using thick targets of polythene, aluminum, iron, copper, zinc, tin, silver, tungsten, and lead for five ..beta.. emitters, viz., /sup 35/S, /sup 147/Pm, /sup 204/Tl, /sup 32/P, and /sup 90/Sr-/sup 90/Y. Effects of geometry and ..beta..-ray end-point energy have been investigated using a reflection geometry in which the geometry factors were varied by more than 40 and ..beta..-ray energy varied over a range 0.167--2.27 MeV. It is found that the mean value of the index of Z dependence of ..beta..-ray backscattering is 1.840.05 over these regions of geometry and energy. Deviations for soft ..beta.. emitters have been confirmed as due to air absorption. The importance of these results in studies of two-component systems is emphasized.
Sharma, K.K.; Singh, M.
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
Backscattering Suppression in Supersonic 1D Polariton Condensates
NASA Astrophysics Data System (ADS)
We investigate the effect of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the ōhoppingö of the condensate through the disorder. Our results evidence a new mechanism for the strong scattering reduction of polaritons at high speeds.
Tanese, D.; Solnyshkov, D. D.; Amo, A.; Ferrier, L.; Bernet-Rollande, E.; Wertz, E.; Sagnes, I.; LemaŅtre, A.; Senellart, P.; Malpuech, G.; Bloch, J.
Near field modulated backscatter for in vivo biotelemetry
Fully implantable wireless biotelemetry devices have traditionally used active VHF\\/UHF transmitters or load modulation at HF frequencies. HF systems tend to be bandwidth-limited due to low frequency magnetic induction, while active VHF\\/UHF transmitters generally consume a significant amount of power in DC bias current. We show in this paper that UHF near-field backscatter can be used to achieve higher data
Jordan S. Besnoff; Matthew S. Reynolds
Standard-target calibration of an acoustic backscatter system
The standard-target method used to calibrate scientific echo sounders and other scientific sonars by a single, solid elastic sphere is being adapted to acoustic backscatter (ABS) systems. Its first application, to the AQUAscat 1000, is described. The on-axis sensitivity and directional properties of transducer beams at three operating frequencies, nominally 1, 2.5, and 4 MHz, have been determined using a
Kenneth G. Foote; M. A. Martini
DUNBID, the Delft University neutron backscattering imaging detector
In the search for low-metallic land mines, the neutron backscattering technique may be applied if the soil is sufficiently dry. An advantage of this method is the speed of detection: the scanning speed may be made comparable to that of a metal detector.A two-dimensional position sensitive detector is tested to obtain an image of the back scattered thermal neutron radiation.
V. R. Bom; C. W. E. van Eijk; M. A. Ali
Millimeter-wave radar back-scattering from water waves
The paper describes the design and operation of a new ultra-high resolution MM-wave FMCW synthetic aperture radar, which has been used for wave-tank experiments to investigate the imaging mechanisms of internal waves in SAR images and the backscattering mechanisms of a water surface at MM-wave. Two series of experiments have been carried out in LEGI, Grenoble, with mechanically generated waves
Glodina Connan; R. Garello; H. D. Griffiths; P. V. Brennan
Measurement of magnetic field using Rayleigh backscattering in optical fibres
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)
Radar backscattering from breaking wind waves: field observation and modelling
In this article, the results of a field study of the Ka-band (37.5 GHz) radar backscattering from breaking wind waves are presented. Radar and a video camera were simultaneously used to measure the radar cross section (RCS) of the whitecap zone and the characteristics of wave-breaking events. A comparison is made between absolute geometrical lengths, areas and orientations of the
Yury Yu. Yurovsky; Vladimir V. Malinovsky
Radar backscattering from breaking wind waves: field observation and modelling
In this article, the results of a field study of the Ka-band (37.5 GHz) radar backscattering from breaking wind waves are presented. Radar and a video camera were simultaneously used to measure the radar cross section (RCS) of the whitecap zone and the characteristics of wave-breaking events. A comparison is made between absolute geometrical lengths, areas and orientations of the
Yury Yu. Yurovsky; Vladimir V. Malinovsky
Neutral beam species measurements using in situ Rutherford backscatter spectrometry
This work describes a new in situ method for measuring the neutral particle fractions in high-power deuterium neutral beams, used to heat magnetically confined fusion plasmas. Deuterium beams, of variable energies, pulse lengths, and powers up to 47 keV, 100 ms, 1.6 MW, were Rutherford backscattered at 135┬░ from the TiC inner neutral beam armor of the PDX, and detected
H. W. Kugel; R. Kaita; G. Gammel; M. D. Williams
Neutral beam species measurements using in situ Rutherford backscatter spectrometry
This work describes a new in situ method for measuring the neutral particle fractions in high power deuterium neutral beams, used to heat magnetically confined fusion plasmas. Deuterium beams, of variable energies, pulse lengths, and powers up to 47 keV, 100 msec, 1.6 MW, were Rutherford backscattered at 135░ from TiC inner neutral beam armor of the PDX, and detected
H. W. Kugel; R. Kaita; G. Gammel; M. D. Williams
Resonant Rutherford backscattering spectrometry for carbon diffusion in silicon
300 keV C+ ion implantation onto Si(1 0 0) wafers was carried out at temperatures of 400, 500, 550, 600, 650 and 700 ░C. Depth profile of C was determined by resonant Rutherford backscattering spectrometry (RRBS) measurements using 12C(alpha,alpha)12C resonant reaction with the alpha-particle energy of 4.27 MeV. The concentration of the implanted carbon at the surface as a function
K. Saravanan; B. K. Panigrahi; S. Amirthapandian; K. G. M. Nair
Materials analysis with Rutherford Backscattering Spectrometry; Application to catalysts
Rutherford Backscattering Spectrometry (RBS) is shown to be a powerful tool in the analysis of model catalysts. The surface coverage of various metals on thin SiO2 layers on Si and thin Al2O3 layers on Al can be accurately measured while simultaneously depth profiles of the metals are obtained. The scattering technique is briefly reviewed and several applications concerning the preparation
L. J. van IJzendoorn; M. J. A. de Voigt; J. W. Niemantsverdriet
Neutral beam species measurements using insitu Rutherford backscatter spectrometry
This work describes a new insitu method for measuring the neutral particle fractions in high-power deuterium neutral beams, used to heat magnetically confined fusion plasmas. Deuterium beams, of variable energies, pulse lengths, and powers up to 47 keV, 100 ms, 1.6 MW, were Rutherford backscattered at 135░ from the TiC inner neutral beam armor of the PDX, and detected using
H. W. Kugel; R. Kaita; G. Gammel; M. D. Williams
Diffusion of Sr in fluorphlogopite determined by Rutherford backscattering spectrometry
We have measured the diffusivity of Sr in fluorphlogopite in a direction perpendicular to the basal planes (in the c direction). Annealing experiments were performed on single crystals, and most of them at ambient pressure. The penetration profiles of the diffusant were determined by Rutherford backscattering spectrometry. Sr diffusion parallel to c obeys an Arrhenius law, whose equation is:DSr=2.7Ę10?14 exp?13?5900▒3100RTwhere
T. Hammouda; D. J. Cherniak
Resonant Rutherford backscattering spectrometry for carbon diffusion in silicon
300keV C+ ion implantation onto Si(100) wafers was carried out at temperatures of 400, 500, 550, 600, 650 and 700░C. Depth profile of C was determined by resonant Rutherford backscattering spectrometry (RRBS) measurements using 12C(?,?)12C resonant reaction with the ?-particle energy of 4.27MeV. The concentration of the implanted carbon at the surface as a function of inverse of implantation temperature
K. Saravanan; B. K. Panigrahi; S. Amirthapandian; K. G. M. Nair
Characterization of electrochemically polymerized metal phthalocyanines using Rutherford backscattering spectrometry
A new electrochemical polymerization method for producing electronically conductive thin films of metal phthalocyanines has been developed. The thickness and stoichiometric composition of nickelphthalocyanine films produced with this technique have been measured using Rutherford backscattering spectrometry. The film thickness is directly proportional to the number of polymerization cycles in the thickness range of 100-2000 (1015 atoms\\/cm2). Diffusion of the solvent,
E. M. Baum; H. Li; T. F. Guarr; J. D. Robertson
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
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.
Relationships between multipolarized radar backscatter and slash pine stand parameters
NASA Technical Reports Server (NTRS)
Multipolarized L-band (24.5 cm) aircraft radar data was obtained for a primarily forested area in northern Florida. Based on the results of previous studies by Hoffer and Hussin (1989), a swath of medium incidence angle (35-25 deg) data was defined. Three groups of slash pine stands were located in the data: 4- to 17-year-old plantations, 18- to 48-year-old plantations, and 16- to 53-year-old natural stands. Stand data obtained from the forest-products companies operating in the area include age, tree height, diameter-at-breast height, basal area, volume (cords/acre), and density (trees/acre). Each of these stand parameters were compared to each of the four polarizations (HH, VV, VH, and HV) of the radar data for each group of stands. Statistically significant relationships were found between the radar backscatter and the forest stand parameters only for the 4- to 17-year-old slash pine plantation stands. In general, the cross-polarized radar backscatter was more highly correlated with the various stand parameters than the like-polarized backscatter, and the VV-polarized data were more highly correlated than the HH-polarized data.
Hussin, Yousif Ali; Hoffer, Roger M.
Temperature mapping for ultrasound scanner using backscattered changes
NASA Astrophysics Data System (ADS)
MRI and ultrasound scanner are the two main methods used to guide thermal ablation. The superiority of MRI over ultrasound scanner comes from its ability to provide temperature mapping during thermal ablation. This paper describes the relationship between the changes in ultrasound backscattering and the temperature changes during HIFU treatments. Data was acquired during a 120s total treatment time with a duty cycle of 90% (1s HIFU on followed by a 0.1s ultrasound scanner acquisition). A thermocouple was placed at the focal point of the ablated area for correlation measurements. Twenty-three ablations were performed in in vitro livers. An increase in ultrasound backscattering as the tissue temperature increase was noted and correlates well with thermocouple measurements. Radiofrequency signals were used to estimate ultrasound backscattering changes in real-time. A linear relationship between changes in the radiofrequency signal and temperature was observed up to 90░C. These temperature measurements also correlate with the dimensions of ablations produced. This report describes the basics of processing that may be used to provide essential feedback to operators of the state of the tissue during treatment.
Chenot, Jķrķmy; Melodelima, David; Chapelon, Jean-Yves
Challenges in tissue characterization from backscattered intravascular ultrasound signals
NASA Astrophysics Data System (ADS)
Plaque characterization through backscattered intravascular ultrasound (IVUS) signal analysis has been the subject of extensive study for the past several years. A number of algorithms to analyze IVUS images and underlying RF signals to delineate the composition of atherosclerotic plaque have been reported. In this paper, we present several realistic challenges one faces throughout the process of developing such algorithms to characterize tissue type. The basic tenet of ultrasound tissue characterization is that different tissue types imprint their own "signature" on the backscattered echo returning to the transducer. Tissue characterization is possible to the extent that these echo signals can be received, the signatures read, and uniquely attributed to a tissue type. The principal difficulty in doing tissue characterization is that backscattered RF signals originating as echoes from different groups of cells of the same tissue type exhibit no obvious commonality in appearance in the time domain. This happens even in carefully controlled laboratory experiments. We describe the method of acquisition and digitization of ultrasound radiofrequency (RF) signals from left anterior descending and left circumflex coronary arteries. The challenge of obtaining corresponding histology images to match to specific regions-of-interest on the images is discussed. A tissue characterization technique based on seven features is compared to a full spectrum based approach. The same RF and histology data sets were used to evaluate the performances of these two techniques.
Katouzian, Amin; Sathyanarayana, Shashidhar; Li, Wenguang; Thomas, Tom; Carlier, Stķphane G.
Measurement of the spatial backscattering impulse-response at short length-scales with polarized enhanced backscattering (EBS)
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).
Radosevich, Andrew J.; Mutyal, Nikhil N.; Turzhitsky, Vladimir; Rogers, Jeremy D.; Yi, Ji; Taflove, Allen; Backman, Vadim
NASA Astrophysics Data System (ADS)
The ALICE experiment is shown to be well suited for studies of exclusive final states from central diffractive reactions. The gluon-rich environment of the central system allows detailed QCD studies and searches for exotic meson states, such as glueballs, hybrids and new charmonium-like states. It would also provide a good testing ground for detailed studies of heavy quarkonia. Due to its central barrel performance, ALICE can accurately measure the low-mass central systems with good purity. The efficiency of the Forward Multiplicity Detector (FMD) and the Forward Shower Counter (FSC) system for detecting rapidity gaps is shown to be adequate for the proposed studies. With this detector arrangement, valuable new data can be obtained by tagging central diffractive processes.
Lõmsõ, J. W.; Orava, R.
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.
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.
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.
Diffraction Gratings WDM Components
Diffraction grating WDM components have tremendous capability in number of channels (160 channel components and more with\\u000a bi-directionality are commercially available and components with two times more channels have been demonstrated experimentally).\\u000a They have a high free spectral range (typically 775 nm with gratings working in the first order). Small spacing such as 25\\u000a GHz is commercially available and 5
Jean-Pierre Laude
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)
Diffraction before destruction
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.
Chapman, Henry N.; Caleman, Carl; Timneanu, Nicusor
Diffraction before destruction.
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
Parametric (integrated backscatter and attenuation) images constructed using backscattered radio frequency signals (25¢56 MHz) from human aortae in vitro
Quantitative ultrasonic tissue characterization using backscattered high-frequency intravascular ultrasound could provide a basis for the objective identification of lesions in vivo. Representation of local measurements of quantitative ultrasonic parameters in a conventional image format should facilitate their interpretation and thus increase their clinical utility. Toward this goal, the apparent integrated backscatter, the slope of attenuation (25¢56 MHz) and the value
S. Lori Bridal; Paul FornĶs; Patrick Bruneval; GeneviĶve Berger
Stability of austenitic 316L steel against martensite formation during cyclic straining
Solution-annealed AISI 316L steel was fatigued with constant plastic strain amplitudes at room temperature and under various conditions at depressed temperatures down to 113K to reveal its stability against deformation-induced martensite formation. Microstructural changes induced by fatigue were characterized by transmission electron microscopy (TEM), electron channeling contrast imaging (ECCI) and electron backscattering diffraction (EBSD) techniques. Neutron diffraction and magnetic induction
J. Man; K. ObrtlĒk; M. Petrenec; P. Beran; M. Smaga; A. Weidner; J. DluhoÜ; T. Kruml; H. Biermann; D. Eifler; J. Polßk
Optical backscattering in the Arabian SeaŚcontinuous underway measurements of particulate inorganic and organic carbon
NASA Astrophysics Data System (ADS)
Continuous surface measurements of temperature, salinity, fluorescence and optical backscattering were made during R/V Thompson cruise no. TN053 in the northern Arabian Sea ("Bio-Optical cruise"; October-November, 1995). The cruise covered the early NE monsoon period. Optical measurements involved alternate estimates of total backscattering and acidified backscattering approximately every 1.5-2 min (measured after addition of a weak acid to dissolve calcium carbonate). The difference between total and acidified backscattering equals "acid-labile backscattering". Total and acid-labile backscattering were converted to the concentration of particulate organic carbon (POC) and particulate inorganic carbon (PIC; calcium carbonate), respectively, and discrete samples taken along the cruise track were used for calibration. Backscattering data were frequently coherent with temperature, salinity, and density variability. Acid-labile backscattering values revealed that calcium carbonate accounted for 10-40% of the total optical backscattering in the region, and the semi-continuous records demonstrated distinct patches of coccolith-rich water. The northern Arabian Sea had the highest acid-labile backscattering. Results suggest that PIC : POC ratios can vary over about four orders of magnitude. Highest surface values of PIC : POC approached one in several places. We also report qualitative observations of phytoplankton community structure made aboard ship, on fresh samples.
Balch, William M.; Drapeau, David T.; Fritz, Jennifer J.; Bowler, Bruce C.; Nolan, Jessica
Backscattering by nonspherical particles, using the coupled-dipole method: An application in radar meteorology
NASA Astrophysics Data System (ADS)
In the coupled-dipole method, an arbitrary particle is modeled as an array of N polarizable subunits each of which gives rise to only electric dipole radiation. Of all scattering angles, backscattering is the most sensitive to small changes in particle size and shape. The coupled-dipole method's ability and limitations for calculating backscattering are demonstrated. For particles with size parameter less than that associated with the first backscattering minimum, the coupled-dipole method agrees favorably with Mie theory. For particles with larger size parameters, the agreement decreases, but accuracy generally improves by increasing the number of dipolar subunits in the array. Backscattering of 94 GHz Doppler radar by raindrops can be used to infer clear air velocity; backscattering by ice crystals may provide similar information. Backscattering at 94 GHz by randomly oriented ice plates or columns does not agree with backscattering by equal-volume ice spheres for size parameters greater than 0.8. Backscattering depends on zenith angle for ice crystals whose principle axes are confined to the horizontal plane. The relationship between first backscattering minimum and size parameter varies with particle shape and zenith angle. Backscattering of vertically polarized light is more sensitive to the presence of ice columns while horizontally polarized light is more sensitive to ice plates.
Dungey, Clifton E.
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.
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)
Diffraction by fractally serrated apertures
NASA Technical Reports Server (NTRS)
An investigation of light diffracted by irregularly serrated apertures yields a closed-form analytical solution that confirms experimental recording of the diffracted patterns. These serrated apertures are modeled by a fractal function. Examples are given for both sinusoidal and fractal aperture perimeters with varying fractal dimension. Relations between the far-zone diffracted fields and the fractal dimension are examined.
Kim, Y.; Grebel, H.; Jaggard, D. L.
Decontamination of CPA diffraction gratings
Summary form only given. The diffraction gratings are mounted in a vacuum chamber of the compressor. In these conditions the diffraction gratings and other gold coated mirrors illuminated by the laser beam are subjected to carbon contamination, especially on the place of the output beam. This reduces diffraction efficiency of the compressor. The cleaning method used at our 100 TW
E. Gubbini; U. Eichmann; V. Karpov; H. Schonnagel; M. P. Kalachnikov; F. Eggenstein; G. Reichardt
Spectral diffraction efficiency characterization of broadband diffractive optical elements.
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
Spectroscopic diffraction phase microscopy.
We present spectroscopic diffraction phase microscopy (sDPM) as a method capable of measuring quantitative phase images at multiple wavelengths. sDPM uses a spatial light modulator at the Fourier plane of a lens to select desired wavelengths from the white light illumination of a grating. The quantitative phase information at different wavelengths allows us to decouple the refractive index and the thickness from the phase shift induced by biological cells. We demonstrate the capability of the setup by dispersion measurements of microsphere beads and RBCs. PMID:23381283
Pham, Hoa; Bhaduri, Basanta; Ding, Huafeng; Popescu, Gabriel
Evaluation of a compact sensor for backscattering and absorption.
Seawater inherent optical properties (IOPs) are key parameters in a wide range of applications in environmental studies and oceanographic research. In particular, the absorption coefficient (a) is the typical IOP used to obtain the concentration of chlorophyll-a in the water-a critical parameter in biological oceanography studies and the backscattering coefficient (b(b)) is used as a measure of turbidity. In this study, we test a novel instrument concept designed to obtain both the absorption and backscattering coefficients. The instrument would emit a collimated monochromatic light beam into the water retrieving the backscattered light intensity as a function of distance from the center of illumination. We use Monte Carlo modeling of light propagation to create an inversion algorithm that translates the signal from such an instrument into values of a and b(b). Our results, based on simulations spanning the bulk of natural values of seawater IOP combinations, indicate that a 6.2 cm diameter instrument with a radial resolution of 1 cm would be capable of predicting b(b) within less than 13.4% relative difference and a within less than 57% relative difference (for 90% of the inverted a values, the relative errors fall below 29.7%). Additionally, these errors could be further reduced by constraining the inversion algorithm with information from concurrent measurements of other IOPs. Such a compact and relatively simple device could have multiple applications for in situ optical measurements, including a and b(b) retrievals from instrumentation mounted on autonomous underwater vehicles. Furthermore, the same methodology could possibly be used for an out-of-water sensor. PMID:21772357
Bogdan, Alina Gainusa; Boss, Emmanuel S
Relating the radar backscattering coefficient to leaf-area index
NASA Technical Reports Server (NTRS)
The relationship between the radar backscattering coefficient of a vegetation canopy, sigma(0) sub can, and the canopy's leaf area index (LAI) is examined. The relationship is established through the development of a model for corn and sorghum and another for wheat. Both models are extensions of the cloud model of Attema and Ulaby (1978). Analysis of experimental data measured at 8.6, 13.0, 17.0, and 35.6 GHz indicates that most of the temporal variations of sigma(0) sub can can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.
Ulaby, F. T. (principal investigator); Allen, C.; Eger, G.; Kanemasu, E.
Confocal backscatter laser velocimeter with on-axis sensitivity.
NASA Technical Reports Server (NTRS)
A confocal backscatter laser Doppler velocimeter (LDV) that measures two velocity components has been developed. This device requires only two incident beams polarized normally to one another. Moreover, the velocity components sensed are nearly orthogonal. The velocimeter employs a combined dual-scatter, local oscillator arrangement to obtain the bidirectional sensitivity. Two photodetectors are used, each sensing only one Doppler frequency proportional to one of the very nearly orthogonal velocity components. In addition, a single Bragg cell serves to frequency bias both velocity components in order to eliminate directional ambiguity. A differencing technique has also been incorporated to enhance the dual-scatter Doppler signal corresponding to the transverse velocity.
Orloff, K. L.; Logan, S. E.
Coherent Backscattering in the Cross-Polarized Channel
NASA Technical Reports Server (NTRS)
We analyze the asymptotic behavior of the cross-polarized enhancement factor in the framework of the standard low-packing-density theory of coherent backscattering by discrete random media composed of spherically symmetric particles. It is shown that if the particles are strongly absorbing or if the smallest optical dimension of the particulate medium (i.e., the optical thickness of a plane-parallel slab or the optical diameter of a spherically symmetric volume) approaches zero, then the cross-polarized enhancement factor tends to its upper-limit value 2. This theoretical prediction is illustrated using direct computer solutions of the Maxwell equations for spherical volumes of discrete random medium.
Mischenko, Michael I.; Mackowski, Daniel W.
Prototype backscatter Moessbauer spectrometer for measurement of Martian surface mineralogy
NASA Technical Reports Server (NTRS)
We have designed and successfully tested a prototype of a backscatter Moessbauer spectrometer (BaMS) targeted for use on the Martian surface to (1) determine oxidation states of iron, and (2) identify and determine relative abundances of iron-bearing mineralogies. No sample preparation is required to perform measurements; it is only necessary to bring sample and instrument into physical contact. The prototype meets our projected specification for a flight instrument in terms of mass, power, and volume. A Moessbauer spectrometer on the Martian surface would provide wide variety of information about the current state of the Martian surface, and this information is described.
Shelfer, T. D.; Morris, R. V.; Agresti, D. G.; Nguyen, T.; Wills, E. L.; Shen, M. H.
Backscattering from dental restorations and splint materials during therapeutic radiation
Models were constructed to simulate as closely as possible the human oral cavity. Radiation absorbed doses were determined for controls and various test situations involving the presence of dental restorative and splint materials during cobalt-60 irradiation of the models. Adjacent gold full crowns and adjacent solid dental silver amalgam cores both increased the dose to the interproximal gingivae by 20%. Use of orthodontic full bands for splinting the jaws increased the dose to the buccal tissues by an average of 10%. Augmentation of dose through backscatter radiation was determined to be only slight for intracoronal amalgam fillings and stainless steel or plastic bracket splints.
Farman, A.G.; Sharma, S.; George, D.I.; Wilson, D.; Dodd, D.; Figa, R.; Haskell, B.
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.
Inelastic Electron Backscattering in a Generic Helical Edge Channel
NASA Astrophysics Data System (ADS)
We evaluate the low-temperature conductance of a weakly interacting one-dimensional helical liquid without axial spin symmetry. The lack of that symmetry allows for inelastic backscattering of a single electron, accompanied by forward scattering of another. This joint effect of weak interactions and potential scattering off impurities results in a temperature-dependent deviation from the quantized conductance, ?G?T4. In addition, ?G is sensitive to the position of the Fermi level. We determine numerically the parameters entering our generic model for the Bernevig-Hughes-Zhang Hamiltonian of a HgTe/CdTe quantum well in the presence of Rashba spin-orbit coupling.
Schmidt, Thomas L.; Rachel, Stephan; von Oppen, Felix; Glazman, Leonid I.
Backscattering by hexagonal ice crystals of cirrus clouds.
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
Statistical Parameter Estimation in Ultrasound Backscattering from Tissue Mimicking Media.
NASA Astrophysics Data System (ADS)
Several tissue characterization parameters, including the effective scatterer number density and the backscatter coefficient, were derived from the statistical properties of ultrasonic echo signals. The effective scatterer number density is the actual scatterer number density in a medium multiplied by a frequency-dependent factor that depends on the differential scattering cross-sections of all scatterers. The method described in this thesis for determining the scatterer number density explicitly retains both the temporal nature of the data acquisition and the properties of the ultrasound field in the data reduction. Moreover, it accounts for the possibility that different sets of scatterers may dominate the echo signal at different frequencies. The random processes involved in forming ultrasound echo signals from random media give rise to an uncertainty in the estimated effective scatterer number density. This uncertainty is evaluated using error propagation. The statistical uncertainty depends on the effective number of scatterers contributing to the segmented echo signal, increasing when the effective number of scatterers increases. Tests of the scatterer number density data reduction method and the statistical uncertainty estimator were done using phantoms with known ultrasound scattering properties. Good agreement was found between measured values and those calculated from first-principles. The properties of the non-Gaussian and non-Rayleigh parameters of ultrasound echo signals are also studied. Both parameters depend on the measurement system, including the transducer field and pulse frequency content, as well as on the medium's properties. The latter is expressed in terms of the scatterer number density and the second and fourth moments of the medium's scattering function. A simple relationship between the non-Gaussian and non-Rayleigh parameters is derived and verified experimentally. Finally, a reference phantom method is proposed for measuring the effective scatterer number density in vivo. Various groups are using the frequency dependent backscatter coefficient (or the spatial autocorrelation function) to characterize scatterer sizes in biological tissue. Generally, sparse scatterer concentrations are assumed in relating scattering parameters to this tissue property. For dense scattering media, we study whether the frequency dependent backscatter coefficient changes with the scatterer volume fraction. Two scattering models suggested by Debye and Yagi are reviewed. In these models, the spatial autocorrelation function describing mass density and compressibility fluctuations in the scattering medium has a characteristic length that depends on the scatterer volume fraction as well as the scatterer size. The models predict the frequency dependence of the backscatter coefficient will vary with the scatterer volume fraction. Qualitative agreement between the model predictions and experimental results are seen for sephadex-in-agar phantoms.
Chen, Jian-Feng
A new inversion algorithm for backscatter ionogram and its experimental validation
NASA Astrophysics Data System (ADS)
Oblique backscatter sounding is a powerful tool for detecting and monitoring the ionosphere continuously at a remote distance. High-frequency (HF) backscatter ionograms provide the amplitudes of backscatter signals with respect to group path or time delay against operating frequency. Application of inversion algorithm to a backscatter ionogram can extract useful information regarding the ionospheric electron density along the propagation paths. The present study proposes a new inversion algorithm on basis of simulated annealing method to acquire the leading edge of sweep-frequency ionogram, which is subsequently validated by ionospheric vertical sounding data. Quantitative comparisons between the vertical sounding measurements and the inversion results obtained from oblique backscatter sounding indicate that the new algorithm enables us to overcome the instability issue that traditional inversion algorithm faces and output reliable information of ionospheric inversion with satisfactory efficiency, thus providing a robust alternative for ionospheric detection based on oblique backscatter ionograms especially when the ionosphere is calm with slow changes.
Zhao, J. J.; Zhou, C.; Yang, G. B.; Jiang, C. H.; Chang, S. S.; Zhu, P.; Gu, X. D.; Ni, B. B.; Zhao, Z. Y.
Radiation damping effects on the ultrashort x-ray pulses generated by nonlinear Thomson backscattering
NASA Astrophysics Data System (ADS)
Nonlinear Thomson backscattering of an intense Gaussian laser pulse by a counterpropagating energetic electron is investigated by numerically solving the electron equation of motion taking into account the radiative damping force. The backscattered radiation characteristics are different for linearly and circularly polarized lasers because of a difference in their ponderomotive forces acting on the electron. The radiative electron energy loss weakens the backscattered power, breaks the symmetry of the backscattered-pulse profile, and prolongs the duration of the backscattered radiation. With the circularly polarized laser, an adjustable double-peaked backscattered pulse can be obtained. Such a profile has potential applications as a subfemtosecond x-ray pump and probe with adjustable time delay and power ratio.
Cang, Yu; Wu, Hui-Chun; Zheng, Jun; Xu, Han; Tian, You-Wei; Yu, Wei
Atmospheric backscatter vertical profiles at 9.2 and 10.6 microns - A comparative study
NASA Technical Reports Server (NTRS)
The paper reports a series of atmospheric aerosol backscatter measurements at two widely spaced CO2 laser wavelengths: 9.25 and 10.6 microns. Comparisons are made between backscatter coefficient profiles at these two wavelengths up to 20-km altitude. Measurements such as those reported here can be used to assess the feasibility of coherent CO2 lidar for wind measurements, and they also provide a partial test of backscatter model predictions.
Ancellet, Gerard M.; Menzies, Robert T.; Tratt, David M.
Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays
Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.
Kuwabara, H. [IHI Corporation, 1, Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501 (Japan)] [IHI Corporation, 1, Shin-Nakahara-cho, Isogo-ku, Yokohama 235-8501 (Japan); Mori, Y.; Kitagawa, Y. [The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsucho, Nishiku, Hamamatsu, Shizuoka 431-1202 (Japan)] [The Graduate School for the Creation of New Photonics Industries, 1955-1 Kurematsucho, Nishiku, Hamamatsu, Shizuoka 431-1202 (Japan)
Monte carlo simulation of the coaxial electrons backscattering from thin films
By using the Monte Carlo method, we simulated the trajectories of coaxial backscattering electrons corresponding to a new\\u000a type of scanning electron microscope. From the calculated results, we obtain a universal expression, which describes with\\u000a good accuracy the backscattering coefficient versus film thickness under all conditions used. By measuring the coaxial backscattering\\u000a coefficient and using this universal formula, the thickness
Hu Da-ping
Standoff detection of hidden objects using backscattered ultra-intense laser-produced x-rays
NASA Astrophysics Data System (ADS)
Ultra-intense laser-produced sub-ps X-ray pulses can detect backscattered signals from objects hidden in aluminium containers. Coincident measurements using primary X-rays enable differentiation among acrylic, copper, and lead blocks inside the container. Backscattering reveals the shapes of the objects, while their material composition can be identified from the modification methods of the energy spectra of backscattered X-ray beams. This achievement is an important step toward more effective homeland security.
Kuwabara, H.; Mori, Y.; Kitagawa, Y.
Characterization of polycrystals with elongated duplex microstructure by inversion of ultrasonic backscattering data
In this letter a simple analytical ultrasonic backscattering model is proposed for determination of characteristic microstructural scales in polycrystalline materials with elongated grains. The inversion methodology for microstructural parameters is based on backscattering coefficient ratios measured in different propagation directions. The ultrasonic backscattering measurements were performed on a Ti alloy sample with a duplex microstructure and the model was applied to experimental data inversion to size the material microtexture.
Lobkis, O. I.; Rokhlin, S. I. [Department of Materials Science and Engineering, Edison Joining Technology Center, Ohio State University, 1248 Arthur E. Adams Dr., Columbus, Ohio 43221 (United States)
Comparison of Lidar Backscatter with Particle Distribution and GOES-7 Data in Hurricane Juliette
NASA Technical Reports Server (NTRS)
Measurements of calibrated backscatter, using two continuous wave Doppler lidars operating at wavelengths 9.1 and 10.6 micrometers were obtained along with cloud particle size distributions in Hurricane Juliette on 21 September 1995 at altitude approximately 11.7 km. Agreement between backscatter from the two lidars and with the cloud particle size distribution is excellent. Features in backscatter and particle number density compare well with concurrent GOES-7 infrared images.
Jarzembski, Maurice A.; Srivastava, Vandana; McCaul, Eugene W., Jr.; Jedlovec, Gary J.; Atkinson, Robert J.; Pueschel, Rudolf F.; Cutten, Dean R.
Computation of clear-air radar backscatter from numerical simulations of turbulence: 2. Backscatter moments throughout the lifecycle of a Kelvin-Helmholtz instability
NASA Astrophysics Data System (ADS)
Franke et al. (2011) describe a numerical simulation of the instability and turbulent breakdown of Kelvin-Helmholtz (KH) billows at a high Reynolds number, numerical assessment of radar backscatter, and accuracies of inferred Doppler spectral moments for one test volume. Those results suggest a potential for significant measurement biases for radars that obtain backscatter from refractive index fluctuations. We present in this paper the morphology of computed radar moments throughout the KH instability lifecycle for two radar configurations in order to reveal the evolving character of radar backscatter and compare the radar velocity estimates with true velocities throughout the evolution, and to provide guidance, and cautions, for the interpretation of these dynamics in observational data. Results reveal strong variations in backscatter moments and character, and dependence on radar measurement parameters, that should be beneficial in the interpretation of such measurements in the atmosphere. Backscatter power predictions agree reasonably with observations of such events and their temporal evolutions. Our results also reveal a potential for significant measurement or sensitivity biases, some of which were predicted previously. Examples include a lack of significant backscatter power in well-mixed billow cores, suggesting possibly weak turbulence where in fact it may be strongest, maximum backscatter power in the billow exteriors, where refractive index fluctuations are large but turbulence is weak, underestimated vertical velocities within the KH billows at early times, and inferred significant vertical velocities where true vertical velocities are near zero at late stages of restratification, especially in the edge regions of the turbulence layer.