These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

Microsoft Academic Search

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

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

2006-01-01

2

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

PubMed

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

2002-03-01

3

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

Microsoft Academic Search

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

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

2006-01-01

4

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

5

Quantitative metallography by electron backscattered diffraction.  

PubMed

Although electron backscattered diffraction (EBSD) in the scanning electron microscope is used mainly to investigate the relationship between local textures and microstructures, the technique has now developed to the stage where it requires serious consideration as a tool for routine quantitative characterization of microstructures. This paper examines the application of EBSD to the characterization of phase distributions, grain and subgrain structures and also textures. Comparisons are made with the standard methods of quantitative metallography and it is shown that in many cases EBSD can produce more accurate and detailed measurements than the standard methods and that the data may sometimes be obtained more rapidly. The factors which currently limit the use of EBSD for quantitative microstructural characterization, including the speed of data acquisition and the angular and spatial resolutions, are discussed, and future developments are considered. PMID:10460682

Humphreys

1999-09-01

6

Chirality determination of quartz crystals using Electron Backscatter Diffraction.  

PubMed

We demonstrate the determination of crystal chirality using electron backscatter diffraction (EBSD) in the scanning electron microscope. The chirality of ?-quartz as a space-group-dependent property is verified via direct comparison of experimental diffraction features to simulations using the dynamical theory of electron diffraction. PMID:25436930

Winkelmann, Aimo; Nolze, Gert

2014-11-20

7

Detail Extraction from Electron Backscatter Diffraction Patterns  

NASA Astrophysics Data System (ADS)

Cross-correlation based analysis of electron backscatter diffraction (EBSD) patterns and the use of simulated reference patterns has opened up entirely new avenues of insight into local lattice properties within EBSD scans. The benefits of accessing new levels of orientation resolution and multiple types of previously inaccessible data measures are accompanied with new challenges in characterizing microscope geometry and other error previously ignored in EBSD systems. The foremost of these challenges, when using simulated patterns in high resolution EBSD (HR-EBSD), is the determination of pattern center (the location on the sample from which the EBSD pattern originated) with sufficient accuracy to avoid the introduction of phantom lattice rotations and elastic strain into these highly sensitive measures. This dissertation demonstrates how to greatly improve pattern center determination. It also presents a method for the extraction of grain boundary plane information from single two-dimensional surface scans. These are accomplished through the use of previously un-accessed detail within EBSD images, coupled with physical models of the backscattering phenomena. A software algorithm is detailed and applied for the determination of pattern center with an accuracy of ˜0.03% of the phosphor screen width, or ˜10?m. This resolution makes it possible to apply a simulated pattern method (developed at BYU) in HR-EBSD, with several important benefits over the original HR-EBSD approach developed by Angus Wilkinson. Experimental work is done on epitaxially-grown silicon and germanium in order to gauge the precision of HR-EBSD with simulated reference patterns using the new pattern center calibration approach. It is found that strain resolution with a calibrated pattern center and simulated reference patterns can be as low as 7x10-4. Finally, Monte Carlo-based models of the electron interaction volume are used in conjunction with pattern-mixing-strength curves of line scans crossing grain boundaries in order to recover 3D grain boundary plane information. Validation of the approach is done using 3D serial scan data and coherent twin boundaries in tantalum and copper. The proposed method for recovery of grain boundary plane orientation exhibits an average error of 3 degrees.

Basinger, Jay

8

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

PubMed Central

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

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

2013-01-01

9

Electron backscatter diffraction: applications for nuclear materials.  

PubMed

The diffraction of electrons was first observed in 1928 by Kikuchi. The phenomenon results in the formation of characteristic diagrams of the crystalline lattice and the orientation of the phase. Backscattered electrons are diffracted by the different crystallographic planes (hkl) according to the Bragg angle thetab. These describe, by symmetry, two cones of axes normal to the diffracting plane. Information is collected on a phosphor screen, leading to the acquisition of a diffraction pattern called a Kikuchi diagram. Several improvements now give a wide range of applications such as phase identification (carbides or complex compounds in a (U,Zr,O) structure), analysis of materials interfaces (ZrO2/UO2), as well as solidification studies and local texture determination (molybdenum sheets). In these applications, EBSD, as a type of quantitative metallography, is a powerful tool. PMID:10460689

Medevielle; Hugon; Dugne

1999-09-01

10

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

Microsoft Academic Search

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

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

2007-01-01

11

High-resolution elastic strain measurement from electron backscatter diffraction patterns: New levels of sensitivity  

Microsoft Academic Search

In this paper, we demonstrate that the shift between similar features in two electron backscatter diffraction (EBSD) patterns can be measured using cross-correlation based methods to ±0.05 pixels. For a scintillator screen positioned to capture the usual large solid angle employed in EBSD orientation mapping this shift corresponds to only ?8.5×10?5rad at the pattern centre. For wide-angled EBSD patterns, the

Angus J. Wilkinson; Graham Meaden; David J. Dingley

2006-01-01

12

Electron backscatter diffraction on femtosecond laser sulfur hyperdoped silicon  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

13

Ion beam polishing for three-dimensional electron backscattered diffraction.  

PubMed

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

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

2013-01-01

14

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.

2014-03-01

15

Orientation precision of electron backscatter diffraction measurements near grain boundaries.  

PubMed

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

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

2014-06-01

16

Present State of Electron Backscatter Diffraction and Prospective Developments  

SciTech Connect

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

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

2008-10-24

17

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

PubMed

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

Payton, E J; Nolze, G

2013-08-01

18

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

Microsoft Academic Search

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

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

2007-01-01

19

Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction  

SciTech Connect

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

2008-01-01

20

Microstructure Characterization of Magnetic-Pulse-Welded AA 6061-T6 by Electron Backscattered Diffraction  

Microsoft Academic Search

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

Yuan Zhang; Suresh Babu; P Zhang; Edward A Kenik; Glenn Daehn

2008-01-01

21

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

22

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

PubMed Central

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

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

2014-01-01

23

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

SciTech Connect

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

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

1999-05-10

24

Quantifying recrystallization by electron backscatter diffraction.  

PubMed

The use of high-resolution electron backscatter diffraction in the scanning electron microscope to quantify the volume fraction of recrystallization and the recrystallization kinetics is discussed. Monitoring the changes of high-angle grain boundary (HAGB) content during annealing is shown to be a reliable method of determining the volume fraction of recrystallization during discontinuous recrystallization, where a large increase in the percentage of high-angle boundaries occurs during annealing. The results are shown to be consistent with the standard methods of studying recrystallization, such as quantitative metallography and hardness testing. Application of the method to a highly deformed material has shown that it can be used to identify the transition from discontinuous to continuous recrystallization during which there is no significant change in the percentage of HAGB during annealing. PMID:15009691

Jazaeri, H; Humphreys, F J

2004-03-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

26

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

SciTech Connect

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

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

2014-03-09

27

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.

2012-10-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

29

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

Microsoft Academic Search

Microstructure evolution of AZ31 Mg alloy during equal channel angular extrusion (ECAE) was investigated by electron back-scattered diffraction (EBSD). The grains of AZ31 Mg alloy were refined significantly after ECAE 1–8 passes at 498K and the distributions of grain size tended to be more uniform with pass number increasing. Frequency of sub-boundaries and low angle grain boundaries (LAGBs) increased at

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

2006-01-01

30

Electron Backscatter Diffraction Analysis of a CZT Growth Tip from a Vertical Gradient Freeze Furnace  

SciTech Connect

Electronic 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-cm2 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 <110> and <112> directions. In some regions, the (001) poles of the CZT matrix aligned with the growth direction, while twins aligned such that (111) and (112) poles aligned with the growth direction. In some other areas, (112) or (011) poles of the CZT matrix aligned with the growth direction. New relationships between the CZT matrix and large Te polycrystalline particles were revealed: {11 }CZT??{1 00}Te and {001}CZT??{0 1}Te.

Sundaram, S. K.; Henager, Charles H.; Edwards, Danny J.; Schemer-Kohrn, Alan L.; Bliss, Mary; Riley, Brian J.

2011-08-15

31

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

PubMed

Due to its very low hardness and atomic number, pure lithium cannot be prepared by conventional methods prior to scanning electron microscopy analysis. Here, we report on the characterization of pure lithium metallic sheets used as base electrodes in the lithium-ion battery technology using electron backscatter diffraction (EBSD) and X-ray microanalysis using energy dispersive spectroscopy (EDS) after the sheet surface was polished by broad argon ion milling (IM). No grinding and polishing were necessary to achieve the sufficiently damage free necessary for surface analysis. Based on EDS results the impurities could be characterized and EBSD revealed the microsctructure and microtexture of this material with accuracy. The beam damage and oxidation/hydration resulting from the intensive use of IM and the transfer of the sample into the microscope chamber was estimated to be <50 nm. Despite the fact that the IM process generates an increase of temperature at the specimen surface, it was assumed that the milling parameters were sufficient to minimize the heating effect on the surface temperature. However, a cryo-stage should be used if available during milling to guaranty a heating artefact free surface after the milling process. Microsc. Res. Tech., 78:30?39, 2015. © 2014 Wiley Periodicals, Inc. PMID:25280344

Brodusch, Nicolas; Zaghib, Karim; Gauvin, Raynald

2015-01-01

32

Electron imaging with an EBSD detector.  

PubMed

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

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

2015-01-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

34

Advanced Characterization of Slags and Refractory Bricks Using Electron Backscatter Diffraction  

SciTech Connect

Numerous studies have been conducted to determine changes that occur in slag that cause a rapid change in viscosity, but these studies have been limited by the inability to characterize/identify the phases present in the slag. Rapid freezing of slag in entrained gasifiers and slagging combustion systems can cause a shutdown of the system. The reactions occurring in slag that result in rapid freezing of slags are not well understood. It is believed that electron backscatter diffraction (EBSD) can be used to analyze slags and aid in their characterization although its use has not been found in literature. The EBSD technique allows particle-by-particle mineralogy based on diffraction patterns generated by the electron beam when the sample is tilted to a high angle. The diffraction pattern (Kikuchi bands) can only come from crystalline phases, which makes this technique ideally suited to study crystal formation in slags where oftentimes the crystals are very small and a reasonable chemical analysis cannot be made by conventional energy-dispersive spectrometry (EDS) methods in the scanning electron microscope. The ability to have mineralogical data based on the crystalline structure of a phase rather than a chemical analysis by EDS allows much better interpretation of the temperature regimes in which specific phases tend to form. Knowing the type and relative amounts of a phase crystallizing in a slag is critical in predicting the viscosity of a slag at a given temperature. Six slag samples were selected based on the parent coal. Unfortunately, none of the slags appeared to have any crystalline material associated with them. The funding for this project was not adequate for generating more slags from the various coal types. For this reason, sample archives were searched for those containing slags that were not rapidly quenched. A slag from a bituminous coal was found to contain several dendritic crystals (10 {mu}m to 50 {mu}m in size) that formed near the edges of the slag. Analysis of these crystals identified the crystalline phase epidote - Ca{sub 2}Al{sub 2}O(Al, Fe{sup 3+})OH(Si{sub 2}O{sub 7})(SiO{sub 4}). The identification could not have been performed from EDS alone because of Ca deficiency. However, looking at the crystal structure combined with EDS shows that the phase present is a Ca-deficient epidote. From this information, a temperature range of formation was determined. This gives a good example of the additional clarity that can be derived from utilizing EBSD. Evaluation of corrosion products by EBSD at the refractory brick and slag interface did reveal penetration and corrosion of slag into the brick through examination of crystalline phases alone. The degree of corrosion was dependent on the type of refractory and chemical makeup of the slag. This technique has not been used before to analyze slags and slag/refractory interactions. More work needs to be performed to better utilize EBSD for this type of analysis. This project demonstrates that the method is a valid technique that can be used to characterize slags and their interactions with refractory materials.

John Kay; Kurt Eylands

2007-09-30

35

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

PubMed

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

Bandli, Bryan R; Gunter, Mickey E

2014-12-01

36

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.

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

2011-09-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

38

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

39

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

PubMed

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

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

2012-06-01

40

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

Microsoft Academic Search

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

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

2007-01-01

41

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

NSDL National Science Digital Library

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

Little, Bethany

2007-08-29

42

Crystallographic Orientation of Cuttlebone Shield Determined by Electron Backscatter Diffraction  

NASA Astrophysics Data System (ADS)

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

Cusack, Maggie; Chung, Peter

2014-01-01

43

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

Microsoft Academic Search

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

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

2006-01-01

44

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

PubMed

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

Batista, L; Rabe, U; Hirsekorn, S

2014-11-01

45

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

PubMed

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

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

2014-07-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

47

Electron backscatter diffraction analysis of Nb3Al multifilamentary strands prepared by rapid heating, quenching and transformation annealing  

NASA Astrophysics Data System (ADS)

To enhance the non-Cu critical current density Jc at 15 T and 4.2 K (1000 A mm - 2 at present) we have endeavoured to refine the grain size of rapid heating, quenching and transformation (RHQT)-processed Nb3Al. In the present study, the grain boundary structures of RHQT-processed Nb3Al were examined by electron backscatter diffraction (EBSD) because transgranular fracture prevents the observation of fractured cross sections of Nb3Al to statistically determine the grain size. The grain size distributions of body-centred-cubic supersaturated-solid-solution Nb(Al)ss and A15 Nb3Al filaments were measured for grains misoriented by more than 2°, 5° and 15°. A mixed grain structure, which consists of a few large grains (>25 µm) and many small grains (<1 µm), was observed for an Nb3Al filament that had been transformed from non-deformed Nb(Al)ss. Plastic deformation that had been made between the rapid heating and quenching steps and the transformation step apparently homogenized the grain size distribution and then reduced the average grain size. The misorientation angle distributions of Nb(Al)ss and Nb3Al were also measured and compared with each other. A clear relationship between the Jc and the inverse grain size was not confirmed for the RHQT Nb3Al conductors examined in the present study, which indicates the importance of making a filament compositionally homogeneous to obtain a high Jc.

Takeuchi, T.; Tsuchiya, K.; Saeda, M.; Banno, N.; Kikuchi, A.; Iijima, Y.

2010-12-01

48

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

49

Zirconium deformation behavior: insights from EBSD measurements.  

SciTech Connect

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

2001-01-01

50

Comparison of recrystallisation kinetics determined by stress relaxation, double hit, optical metallography and EBSD approaches  

Microsoft Academic Search

A comparison of the recrystallisation kinetics determined by stress relaxation (SR), double-hit (DH), optical metallography and scanning electron microscope\\/electron backscattered diffraction (SEM\\/EBSD) mapping experimental approaches has been conducted. Two different types of steel were used as experimental material: C–Mn and interstitial-free (IF). Tests were carried out in the austenitic region for C–Mn steel and just above the Ar1 temperature for

M. Dzubinsky; Z. Husain; W. M. van Haaften

2004-01-01

51

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

NASA Astrophysics Data System (ADS)

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

Michalska, J.; Chmiela, B.

2014-03-01

52

Critical comparison of dislocation boundary alignment studied by TEM and EBSD: technical issues and theoretical consequences  

SciTech Connect

The plane of extended deformation induced boundaries (geometrically necessary boundaries) determined by transmission electron microscopy (TEM) has previously been found to be grain orientation dependent so that some grains have boundaries aligned with slip planes while others do not. However, in both types of grains the boundaries are aligned with macroscopic planes. A recently published analysis by electron backscattered diffraction (EBSD) found no evidence for alignment of boundaries with slip planes or any other simple crystallographic plane, i.e. only macroscopic alignment. This discrepancy is discussed based on a critical comparison of the TEM and EBSD based techniques and TEM observations of boundary planes in grains of selected orientations in cold-rolled aluminium. The latter clearly show that the EBSD finding is incorrect. The present analysis thereby confirms that grain orientation-dependent boundary planes is a general phenomenon.

Winther, G.; Huang, X.; Godfrey, A.; Hansen, N

2004-09-06

53

Novel EBSD preparation method for Cu/Sn microbumps using a focused ion beam  

SciTech Connect

We proposed a novel technique developed from focused ion beam (FIB) polishing for sample preparation of electron backscatter diffraction (EBSD) measurement. A low-angle incident gallium ion beam with a high acceleration voltage of 30 kV was used to eliminate the surface roughness of cross-sectioned microbumps resulting from mechanical polishing. This work demonstrates the application of the FIB polishing technique to solders for a high-quality sample preparation for EBSD measurement after mechanical polishing. - Highlights: Black-Right-Pointing-Pointer The novel FIB technique of sample preparation is fast, effective and low-cost. Black-Right-Pointing-Pointer It can enhance the process precision to the specific area of the sample. Black-Right-Pointing-Pointer It is convenient for analyzing the metallurgy of the microbump in 3DIC packaging. Black-Right-Pointing-Pointer The EBSD image quality can be enhanced by just using a common FIB instrument.

Liu, Tao-Chi; Chen, Chih [National Chiao Tung University, Department of Materials Science and Engineering, Hsinchu 30010, Taiwan, ROC (China)] [National Chiao Tung University, Department of Materials Science and Engineering, Hsinchu 30010, Taiwan, ROC (China); Chiu, Kuo-Jung [Integrated Service Technology Inc., No. 19, Pu-ding Rd., Hsinchu 30072, Taiwan, ROC (China)] [Integrated Service Technology Inc., No. 19, Pu-ding Rd., Hsinchu 30072, Taiwan, ROC (China); Lin, Han-Wen [National Chiao Tung University, Department of Materials Science and Engineering, Hsinchu 30010, Taiwan, ROC (China)] [National Chiao Tung University, Department of Materials Science and Engineering, Hsinchu 30010, Taiwan, ROC (China); Kuo, Jui-Chao, E-mail: jckuo@mail.ncku.edu.tw [National Cheng Kung University, Department of Materials Science and Engineering, Tainan, Taiwan, ROC (China)] [National Cheng Kung University, Department of Materials Science and Engineering, Tainan, Taiwan, ROC (China)

2012-12-15

54

Need for Standardization of EBSD Measurements for Microstructural Characterization of Thin Film Structures  

SciTech Connect

Microstructural characterization of metal thin films includes measurement of grain size, crystallographic texture and misorientation angle across grain boundaries. All of these measurements can be made simultaneously by the use of electron backscatter diffraction (EBSD) in the scanning electron microscope. The use of EBSD measurements to characterize microstructure requires the collection and analysis of thousands of individual diffraction patterns, and the extraction of statistical quantities of interest from the data set. The results depend on the particular analytical procedures used. Since the grains in interconnect structures are often much smaller than those in bulk materials, the measurement and reporting protocols require adaptation of procedures developed for bulk materials. Here we demonstrate results from a specific procedure for collecting and analyzing EBSD data on electrodeposited copper films. We show that without careful controls, the apparent grain size can vary by a factor of two or more, and the time required to acquire the data can differ by hours. The demonstrated practical advantages of EBSD over previously available techniques and the severe effect of experimental parameters on the results support the need for standardization of the methods used for microstructural characterization by use of EBSD.

Geiss, Roy H.; Read, David T. [Materials Reliability Division, NIST, Boulder, Colorado 80305 (United States)

2007-09-26

55

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

E-print Network

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

Bascou, Jérôme

56

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

2006-07-01

57

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

SciTech Connect

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

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

2009-04-15

58

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

59

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

60

Utilizing Ebsd to Validate and Understand Nde Techniques  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

61

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

SciTech Connect

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

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

2011-09-15

62

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

PubMed Central

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

Cayron, Cyril

2007-01-01

63

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

SciTech Connect

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

C. J. BOEHLERT

2001-06-01

64

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

65

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

66

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

SciTech Connect

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

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

2009-02-15

67

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

NASA Astrophysics Data System (ADS)

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

Moser, D. E.

2012-12-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

69

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

PubMed

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

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

2013-10-01

70

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

PubMed

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

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

2013-08-01

71

Identification of phases in corium held at high temperature in a tungsten crucible by SEM, EPMA, and EBSD  

SciTech Connect

Heat treatments of U - Zr - O mixtures of different oxygen contents (ranging from 1 to 35 at. %) and of a constant U/Zr ratio (U/Zr = 1.35 which is characteristic of the inner part of a pressurized-water reactor) were performed in order to study the high temperature behavior of corium. The selected U-Zr-O mixtures were put in a tungsten crucible and heated to 2050{degrees}C. The specimens were thereafter analyzed by Scanning Electron Microscopy (SEM), Electron Probe MicroAnalysis (EPMA) and Electron BackScattering Diffraction (EBSD).

Schneider, B.; Bouchet, C.; Perodeaud, P. [DCC/DTE/SIM, Pierrelatte (France)] [and others

1996-12-31

72

Scanning Electron Microscopy/Electron Backscatter Diffraction-Based Observations of Martensite Variant Selection and Slip Plane Activity in Supermartensitic Stainless Steels during Plastic Deformation at Elevated, Ambient, and Subzero Temperatures  

NASA Astrophysics Data System (ADS)

The deformation-induced martensite variant selection in a supermartensitic stainless steel (SMSS) has been examined in the temperature range from -60 °C to 150 °C, using in-situ tensile testing in combination with electron backscatter diffraction (EBSD) analyses in the scanning electron microscope (SEM). In the as-received ( i.e., intercritically annealed) condition, the base material contains about 40 vol pct of retained austenite. At each testing temperature, this austenite transforms back to martensite during plastic deformation at a rate which is controlled by the accumulated plastic strain in the material. On the other hand, the applied strain rate and crystallographic orientations of the prior austenite grains do not affect the overall transformation rate. Moreover, the subsequent Schmid factor analysis reveals that the martensite variant selection is independent of the local slip activity within the austenite. Therefore, no new martensite variants, besides those already present in the parent steel, develop during the phase transformation. At the same time, their individual intensities remain approximately constant within each prior austenite grain. This means that the deformation-induced martensite variants nucleate from the same sites as those that are operative in the intercritically-annealed base material. Thus, the observed variant selection is another example of the inherent reversible nature of the martensite transformation.

Karlsen, Morten; Grong, Øystein; Søfferud, Mario; Hjelen, Jarle; Rørvik, Gisle; Chiron, Remi

2009-02-01

73

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

PubMed

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

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

2005-02-01

74

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

PubMed

Several analytical techniques that are currently available can be used to determine the spatial distribution and amount of austenite, ferrite and precipitate phases in steels. The application of magnetic force microscopy, in particular, to study the local microstructure of stainless steels is beneficial due to the selectivity of this technique for detection of ferromagnetic phases. In the comparison of Magnetic Force Microscopy and Electron Back-Scatter Diffraction for the morphological mapping and quantification of ferrite, the degree of sub-surface measurement has been found to be critical. Through the use of surface shielding, it has been possible to show that Magnetic Force Microscopy has a measurement depth of 105-140nm. A comparison of the two techniques together with the depth of measurement capabilities are discussed. PMID:25195013

Warren, A D; Harniman, R L; Collins, A M; Davis, S A; Younes, C M; Flewitt, P E J; Scott, T B

2015-01-01

75

Depth dependent elastic strain in ZnO epilayer: combined Rutherford backscattering/channeling and X-ray diffraction  

NASA Astrophysics Data System (ADS)

A ZnO layer was grown by metalorganic chemical vapor deposition (MOCVD) on a sapphire (0 0 0 1) substrate. The perpendicular and parallel elastic strain of the ZnO epilayer, e? = 0.19%, e? = -0.29%, respectively, were derived by using the combination of Rutherford backscattering (RBS)/channeling and X-ray diffraction (XRD). The ratio ? e?/ e?? = 1.5 indicates that ZnO layer is much stiffer in the a-axis direction than in the c-axis direction. By using RBS/C, the depth dependent elastic strain was deduced. The strain is higher at the depth close to the interface and decreases towards the surface. The negative tetragonal distortion was explained by considering the lattice mismatch and thermal mismatch in ZnO thin film.

Feng, Zhenxing; Yao, Shude; Hou, Lina; Jin, Ruiqin

2005-03-01

76

EBSD study of substrate-mediated growth of hexagonal boron nitride  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

77

EBSD study of purity effects during hot working in austenitic stainless steels  

Microsoft Academic Search

The technique of electron back scattering diffraction (EBSD) is considered as a powerful instrument for the study of the microstructural changes during hot forming processes and gives the possibility to present the information in different ways (OIM, misorientation diagram and pole figures). The present work is focused on the observation by EBSD of the microstructure evolution during deformation at high

M. El Wahabi; L. Gavard; J. M. Cabrera; J. M. Prado; F. Montheillet

2005-01-01

78

Suppression of backscattered diffraction from sub-wavelength 'moth-eye' arrays.  

PubMed

The eyes and wings of some species of moth are covered with arrays of nanoscale features that dramatically reduce reflection of light. There have been multiple examples where this approach has been adapted for use in antireflection and antiglare technologies with the fabrication of artificial moth-eye surfaces. In this work, the suppression of iridescence caused by the diffraction of light from such artificial regular moth-eye arrays at high angles of incidence is achieved with the use of a new tiled domain design, inspired by the arrangement of features on natural moth-eye surfaces. This bio-mimetic pillar architecture contains high optical rotational symmetry and can achieve high levels of diffraction order power reduction. For example, a tiled design fabricated in silicon and consisting of domains with 9 different orientations of the traditional hexagonal array exhibited a ~96% reduction in the intensity of the -1 diffraction order. It is suggested natural moth-eye surfaces have evolved a tiled domain structure as it confers efficient antireflection whilst avoiding problems with high angle diffraction. This combination of antireflection and stealth properties increases chances of survival by reducing the risk of the insect being spotted by a predator. Furthermore, the tiled domain design could lead to more effective artificial moth-eye arrays for antiglare and stealth applications. PMID:23388890

Stavroulakis, Petros I; Boden, Stuart A; Johnson, Thomas; Bagnall, Darren M

2013-01-14

79

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

80

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

NASA Technical Reports Server (NTRS)

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

Martinez, James

2011-01-01

81

Correlated diffraction and fluorescence in the backscattering iridescence of the male butterfly Troides magellanus (Papilionidae).  

PubMed

The male Troides magellanus--a birdwing butterfly that lives in a restricted area of the Philippines--concentrates on its hindwings at least two distinct optical processes that contribute to its exceptional visual attraction. The first is the very bright uniform yellow coloration caused by a pigment which generates yellow-green fluorescence, and the other is a blue-green iridescence which results from light diffraction at grazing emergence under a specific illumination. Detailed optical measurements reveal that these optical effects are correlated, the fluorescence being enhanced by illuminations conditions that favor the occurrence of the iridescence. These effects are analyzed, with the conclusion that both of them depend on the same optical device: a one-dimensional microribs grating which appear on the sides of the ridges that run along the yellow scales. PMID:18850861

Vigneron, Jean Pol; Kertész, Krisztián; Vértesy, Zofia; Rassart, Marie; Lousse, Virginie; Bálint, Zsolt; Biró, László P

2008-08-01

82

Correlated diffraction and fluorescence in the backscattering iridescence of the male butterfly Troides magellanus (Papilionidae)  

NASA Astrophysics Data System (ADS)

The male Troides magellanus—a birdwing butterfly that lives in a restricted area of the Philippines—concentrates on its hindwings at least two distinct optical processes that contribute to its exceptional visual attraction. The first is the very bright uniform yellow coloration caused by a pigment which generates yellow-green fluorescence, and the other is a blue-green iridescence which results from light diffraction at grazing emergence under a specific illumination. Detailed optical measurements reveal that these optical effects are correlated, the fluorescence being enhanced by illuminations conditions that favor the occurrence of the iridescence. These effects are analyzed, with the conclusion that both of them depend on the same optical device: a one-dimensional microribs grating which appear on the sides of the ridges that run along the yellow scales.

Vigneron, Jean Pol; Kertész, Krisztián; Vértesy, Zofia; Rassart, Marie; Lousse, Virginie; Bálint, Zsolt; Biró, László P.

2008-08-01

83

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

84

A study of the initial growth kinetics of the copper-aluminum thin-film interface reaction by insitu x-ray diffraction and Rutherford backscattering analysis  

Microsoft Academic Search

X-ray diffraction and Rutherford backscattering (RBS) analysis were used independently to investigate the interface reaction of Cu-Al thin-film bilayers during insitu annealing in the temperature range 157–220 °C. The growth kinetics of the ?-CuAl2 phase were measured and were found to follow a diffusion limited process. Using Arrhenius plots, activation energies of 1.21 and 1.24 eV and preexponential factors of

R. A. Hamm; J. M. Vandenberg

1984-01-01

85

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

PubMed

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

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

2005-02-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

87

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.

2012-03-01

88

3D EBSD characterization of deformation structures in commercial purity aluminum  

SciTech Connect

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: lnfe@risoe.dtu.dk [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)

2010-11-15

89

Electron backscatter diffraction as a domain analysis technique in BiFeO3-PbTiO3 single crystals  

Microsoft Academic Search

xBiFeO3-(1-x)PbTiO3 single crystals were grown via a flux method for a range of compositions. Presented here is a study of the domain configuration in the 0.5BiFeO3-0.5PbTiO3 composition using electron backscatter diffraction to demonstrate the ability of the technique to map ferroelastic domain structures at the micron and submicron scale. The micron-scale domains exhibit an angle of approximately 85deg between each

Tim L. Burnett; Tim P. Comyn; Eleanor Merson; Andrew J. Bell; Ken Mingard; Tristan Hegarty; Markys Cain

2008-01-01

90

Quantitative metallography of ?-Sn dendrites in Sn3.8Ag0.7Cu ball grid array solder balls via electron backscatter diffraction and polarized light microscopy  

Microsoft Academic Search

Electron backscatter diffraction and polarized light microscopy have been used to quantify the number of crystallographically\\u000a independent ?-Sn dendrites present in near-eutectic, ball grid array Sn-Ag-Cu (SAC) solder balls as a function of cooling\\u000a rate (0.35–3.0C\\/s). Based on these data, it is estimated that a single 900-m-diameter solder ball contains on average eight\\u000a individual ?-Sn dendrites, independent of cooling rate.

A. LaLonde; D. Emelander; J. Jeannette; C. Larson; W. Rietz; D. Swenson; D. W. Henderson

2004-01-01

91

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

PubMed

Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. PMID:25126753

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

2014-12-01

92

Characterization of a ZnO Epilayer Grown on Sapphire by using Rutherford Backscattering/Channeling and X-Ray Diffraction  

NASA Astrophysics Data System (ADS)

A ZnO layer with rather good crystalline quality (?min = 9.4%) is grown on a sapphire substrate by plasma enhanced chemical vapor deposition (PECVD). Rutherford backscattering (RBS)/channeling and high-resolution x-ray diffraction (XRD) are used to characterize the elastic strain in the ZnO epilayer. The tetragonal distortion is positive and depth dependent. It is highest near the interface and decreases towards the sample surface. By combining the results of RBS and XRD, the average elastic strains in the parallel and the perpendicular directions can be calculated to be 0.50% and -0.17%, respectively.

Ding, Bin-Feng

2012-03-01

93

Comparison of recrystallisation kinetics determined by stress relaxation, double hit, optical metallography and EBSD approaches  

SciTech Connect

A comparison of the recrystallisation kinetics determined by stress relaxation (SR), double-hit (DH), optical metallography and scanning electron microscope/electron backscattered diffraction (SEM/EBSD) mapping experimental approaches has been conducted. Two different types of steel were used as experimental material: C-Mn and interstitial-free (IF). Tests were carried out in the austenitic region for C-Mn steel and just above the Ar{sub 1} temperature for IF steel. Both steels were investigated in static and postdynamic recrystallisation (SRx and PDRx, respectively) regions. The work indicates that some differences exist between the results given by these methods. The biggest correction to the experimental results in the SRx region has to be performed on the 'raw data' obtained by the SR method. The SR method, owing to its continually applied stress, tends to accelerate the recrystallisation kinetics. The estimation of the recrystallised fraction in the PDRx region by the DH test gives even higher error because of dynamic changes of microstructure during the second hit.

Dzubinsky, M.; Husain, Z.; Haaften, W.M. van

2004-05-15

94

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

2013-08-01

95

Correlating whisker growth and grain structure on Sn-Cu samples by real-time scanning electron microscopy and backscattering diffraction characterization  

SciTech Connect

Whiskers/hillocks grow out of Pb-free Sn coatings used in electronics manufacturing. To determine which grains form whiskers/hillocks, we use scanning electron microscopy and backscattering diffraction to simultaneously monitor the surface morphology and grain structure. To reduce surface roughness, we developed a ''peel-off'' method to prepare ultra-flat samples that were measured repeatedly while whiskers/hillocks formed. We find grains that form into whiskers/hillocks are present in the as-deposited film (i.e., not re-nucleated) and many have horizontal grain boundaries beneath them. Grain rotation during whisker/hillock formation means that measurements performed after the features grow do not indicate their initial grain orientations.

Pei Fei; Jadhav, Nitin; Chason, Eric [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States)

2012-05-28

96

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

97

A study of the initial growth kinetics of the copper-aluminum thin-film interface reaction by in situ x-ray diffraction and Rutherford backscattering analysis  

NASA Astrophysics Data System (ADS)

X-ray diffraction and Rutherford backscattering (RBS) analysis were used independently to investigate the interface reaction of Cu-Al thin-film bilayers during in situ annealing in the temperature range 157-220 °C. The growth kinetics of the ?-CuAl2 phase were measured and were found to follow a diffusion limited process. Using Arrhenius plots, activation energies of 1.21 and 1.24 eV and preexponential factors of 4×10-1 and 9×10-1 cm2 s-1 were obtained from x-ray diffraction and RBS, respectively. X-ray and RBS data are presented and advantages of each method are discussed. It was observed in the in situ x-ray scans that the phase ?2-Cu9Al4 grows simultaneously with ?-CuAl2 from the beginning of the interface reaction. The growth of ?2-Cu9Al4 is also diffusion limited with an activation energy of 1.59 eV and a preexponential factor of 6×102 cm2 s-1 as obtained from x-ray data. The growth of both phases is believed to be largely controlled by volume diffusion. A comparison with previous studies indicated that depending on the annealing treatment, either ?2-Cu9Al4 or ?1-Cu3Al grows together with ?-CuAl2 in the initial stage of the interface reaction.

Hamm, R. A.; Vandenberg, J. M.

1984-07-01

98

Recrystallization, Grain Growth in Copper Foil at High Temperature Studied By Electron Back Scatter Diffraction  

NASA Astrophysics Data System (ADS)

As-received cold rolled and isothermally re-crystallized textures of high purity copper foil were studied using electron back-scattered diffraction patterns (EBSD) in a scanning electron microscope. The evolution of the re-crystallization texture was investigated as a function of annealing temperature. In as is sample, the Cu grains are small and equi-axed, but re-crystallization results in grains several microns in size. We observe a significant enhancement of the (311) texture by pole figure measurements till annealing temperatures of 400 °C and then enhancement of (200) texture at annealing temperatures of 600 °C. We propose that multiple twinning is the mechanism for this phenomenon.

Tiwari, Pragya; Srivastava, Himanshu; Rai, Sanjay; Deb, S. K.

2011-07-01

99

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

SciTech Connect

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

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

2011-06-01

100

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; Lavallée, Yan; Larsen, Jessica; Mariani, Elisabetta

2014-05-01

101

Diffraction  

NSDL National Science Digital Library

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

2006-07-15

102

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.

2010-12-01

103

Infrared backscattering  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

104

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

2006-12-01

105

Electromagnetic backscattering by corner reflectors  

NASA Technical Reports Server (NTRS)

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

Balanis, C. A.; Griesser, T.

1986-01-01

106

Advanced characterization of twins using automated EBSD  

SciTech Connect

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

Wright, S. I. (Stuart I.); Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Larsen, Ryan J.

2002-01-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

108

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

PubMed

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

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

2015-02-01

109

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

PubMed

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

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

2009-03-01

110

EBSD characterization of pre-Cambrian deformations in conglomerate pebbles (Sierra de la Demanda, Northern Spain)  

NASA Astrophysics Data System (ADS)

Pre-Cambrian and unconformable earliest Cambrian rocks from the Sierra de la Demanda (N Spain) exhibit field and microstructural relationships that attest to orogenic events recorded by concealed basement rocks. Neoproterozoic foliated slates ("Anguiano Schists") crop out under up to 300 m thick, unfoliated quartz-rich conglomerates ("Anguiano Conglomerates") and quartzites which are stratigraphically ca. 600 m below the oldest, paleontologically dated, pre-trilobitic Cambrian layers (likely older than 520 Ma). The Anguiano Conglomerates contain mm to cm grainsized well-rounded pebbles of various types including monocrystalline quartz, detrital zircon and tourmaline-bearing sandstones, black cherts and metamorphic poly-crystalline quartz aggregates. The undeformed matrix is made of much smaller (diagenetically overgrown) monocrystaline quartz grains and minor amounts of accesory zircon, tourmaline and mica. Black chert pebbles exhibit microstructural evidence of brittle deformation (microfaults and thin veins of syntaxial fibrous quartz). These and the fine-grained sandstone pebbles can also exhibit ductile deformations (microfolds with thickened hinges and axial planar continuous foliations), too. Polycrystalline quartz pebbles exhibit a variety of microstructures that resulted from syn-metamorphic ductile deformations. These are recognisable under the petrographic microscope and include continuous foliations, quartz shape fabrics, various types of subgrain or recrystallized new grain microtextures, and lattice preferred orientations (LPOs). Conventional characterization of quartz fabrics (after oriented structural sections) is challenged in conglomerate pebble thin sections by the difficulty of unraveling in them the complete structural reference framework provided by foliation (whose trace can be unraveled) and lineation orientation (which cannot be directly identified). Quartz in various metamorphic polycrystalline pebbles was studied with the Electron Back-Scatter Diffraction (EBSD) technique. The identification of quartz c-axis point maxima or girdles and their geometrical relationships with respect to -axis arrangements and pebble foliation traces enabled us to identify the operation of basal and prism- and occasionally prism-[c] intracrystalline slip systems. This points to upper-greenschists and amphibolite facies syn-metamorphic deformations. By contrast, black chert and sandstone pebbles and matrix quartz aggregates lack any LPO. The source area of the conglomerates was likely a pre-Cambrian basement that contained penetratively deformed low- to medium-grade metamorphic rocks. Radiometric dating of this metamorphism has not been accomplished so far though it is known that inherited Precambrian sources in the Iberian Peninsula relate notably to Neoproterozoic (Pan-African and Cadomian) orogens, and to a lesser extent to Paleoproterozoic (1.8-2.1 Ga) or Neoarchean (2.4-2.8 Ga) ones. Neoproterozoic (Cadomian) metamorphism of this grade has only been recognized in SW Iberia. If the fabrics here studied were Cadomian, they might be related to the arc-related igneous suites that have been detected or inferred in other realms of the northern Iberian Massif.

Puelles, Pablo; Ábalos, Benito; Fernández-Armas, Sergio

2010-05-01

111

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

SciTech Connect

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

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

2014-01-01

112

Quantification of dislocation structure heterogeneity in deformed polycrystals by EBSD  

NASA Astrophysics Data System (ADS)

Plastic deformation in polycrystalline materials involves a complex interaction of dislocations with defects in the lattice. The geometrically necessary component of the dislocation density can be quantified to some extent using data obtained from automated electron backscatter diffraction scans over planar regions or volumes using the three-dimensional imaging techniques that are currently available. Reliable measurements require that the step size of the orientation data used in determination of geometrically necessary dislocation densities be on the scale of the microstructural information. Measurements were performed in deformed Cu, Al and steel specimens. Geometrically necessary dislocation density in Cu deformed 10% in compression was about 15-30% of the overall estimated dislocation density. Measurements in Al demonstrate that three-dimensional estimates are on the order of 1.2-2 times the values obtained from 2D measurements on the same structures. Analysis of interstitial free steel specimens shows an increase in average geometrically necessary dislocation density by an order of magnitude for specimens deformed to 12% tensile deformation elongation.

Field, D. P.; Merriman, C. C.; Allain-Bonasso, N.; Wagner, F.

2012-03-01

113

SEM, EDS, EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys  

SciTech Connect

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: franck.tancret@univ-nantes.fr; Furtado, J. [Air Liquide, Centre de Recherche Claude-Delorme, 1, chemin de la Porte des Loges, 78354 Jouy-en-Josas (France)

2008-11-15

114

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

PubMed

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

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

2009-07-01

115

Conductance quantization and backscattering  

E-print Network

Conductance quantization and backscattering Jens U. Nöckel I. Institut für Theoretische Physik to illustrate that backscattering can occur without any effect on the conductance quantization, which. [17] and Wharam et al. [18] that the conductance of a nanostructured constriction in a two

Nöckel, Jens Uwe

116

EBSD observations of dynamic recrystallization mechanisms in ice.  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

117

Micro-geodynamics of the Karakoram Fault Zone, Ladakh, NW Himalaya.  

E-print Network

??Microgeodynamics relates grain-scale deformation microstructures to macroscopic tectonic processes. Here the microgeodynamic approach combines optical and electron microscopy, including electron backscattered diffraction (EBSD), with field… (more)

Wallis, David

2014-01-01

118

Extracting electron backscattering coefficients from backscattered electron micrographs  

SciTech Connect

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

Zupanic, F., E-mail: franc.zupanic@uni-mb.si

2010-12-15

119

Backscatter Data Map  

USGS Multimedia Gallery

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

120

Radar backscatter modelling  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

121

THERMAL NEUTRON BACKSCATTER IMAGING.  

SciTech Connect

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

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

2004-10-16

122

Measuring Stress Distributions in Ti-6Al-4V Using Synchrotron X-Ray Diffraction  

NASA Astrophysics Data System (ADS)

This article presents a quantitative strain analysis (QSA) study aimed at determining the distribution of stress states within a loaded Ti-6Al-4V specimen. Synchrotron X-rays were used to test a sample that was loaded to a uniaxial stress of 540 MPa in situ in the A2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). Lattice-strain pole figures (SPFs) were measured and used to construct a lattice strain distribution function (LSDF) over the fundamental region of orientation space for each phase. A high-fidelity geometric model of the experiment was used to drastically improve the signal-to-noise ratio in the data. The three-dimensional stress states at every possible orientation of each ? (hcp) and ? (bcc) crystal within the aggregate were calculated using the LSDF and the single-crystal moduli. The stress components varied by 300 to 500 MPa over the orientation space; it was also found that, in general, the crystal stress states were not uniaxial. The maximum shear stress resolved on the basal and prismatic slip systems of all orientations within the ? phase, hat tau _{{text{rss}}} , was calculated to illustrate the utility of this approach for better identifying “hard” and “soft” orientations within the loaded aggregate. Orientations with low values of hat tau _{{text{rss}}} , which are potential microcrack initiation sites during dwell fatigue conditions, are considered hard and were subsequently illustrated on an electron backscatter diffraction (EBSD) map.

Bernier, J. V.; Park, J.-S.; Pilchak, A. L.; Glavicic, M. G.; Miller, M. P.

2008-12-01

123

Electrostatic Backscattering by Insulating Obstacles , L. Wartha  

E-print Network

Electrostatic Backscattering by Insulating Obstacles M. Hankea, , L. Wartha aInstitut f backscatter data for a three dimensional obstacle problem in electrostatics. In particular, we investigate: electrostatics, obstacle problem, backscatter data 1. Introduction Backscatter is a notion for the scattered

Hanke-Bourgeois, Martin

124

Detector for high-energy photon backscatter  

Microsoft Academic Search

High energy photon backscatter uses pair production to probe deep beneath surfaces with single side accessibility or to image thick, radiographically opaque objects. At the higher photon energies needed to penetrate thick and\\/or highly attenuating objects, Compton backscatter becomes strongly forward peaked with relatively little backscatter flux. Furthermore, the downward energy shift of the backscattered photon makes it more susceptible

Michael D. Silver; Joseph W. Erker; Michael Z. Duncan; Thomas J. Hartford; E. A. Sivers; James F. Hopkinson

1993-01-01

125

EBSD characterization of twinning in cold-rolled CP-Ti  

SciTech Connect

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

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

2013-10-15

126

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

SciTech Connect

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

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

2013-08-15

127

CONVEX BACKSCATTERING SUPPORT IN ELECTRIC IMPEDANCE TOMOGRAPHY  

E-print Network

CONVEX BACKSCATTERING SUPPORT IN ELECTRIC IMPEDANCE TOMOGRAPHY MARTIN HANKE, NUUTTI HYV ¨ONEN of the method. Key words. Electric impedance tomography, inclusions, backscattering, backscattering support for the inverse obstacle problem in impedance tomography. Under mild restrictions on the topological prop- erties

Hanke-Bourgeois, Martin

128

Diffraction Theory  

Microsoft Academic Search

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

C J Bouwkamp

1954-01-01

129

Backscatter absorption gas imaging system  

DOEpatents

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

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

1985-01-01

130

Strong Bragg backscattering in reflectometry  

NASA Astrophysics Data System (ADS)

The reflection of the probing microwave occurring in the vicinity of the backscattering Bragg resonance point (far from the cut-off) at a high enough density fluctuation level and leading to a large jump of the reflected wave phase and a corresponding time delay is described analytically using a 1D model. Explicit expressions for the reflection and transmission coefficients are derived and compared against results of numerical modelling. The criteria for transition to the nonlinear regime of strong Bragg backscattering (BBS) is obtained for both O-mode and X-mode reflectometry. It is shown that a strong nonlinear regime of BBS may occur in ITER at the 0.5-2% relative density perturbation level both for the ordinary and extraordinary mode probing. The possibility of probing wave trapping leading to strong enhancement of the electric field and associated high phase variation of the reflected wave due to BBS is demonstrated.

Gusakov, E. Z.; Heuraux, S.; Popov, A. Yu

2009-06-01

131

Squiral diffraction  

E-print Network

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

Uwe Grimm; Michael Baake

2012-11-23

132

Shock Recrystallisation and Decomposition of Zircon  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

133

Phase-Transformation-Induced Twins in Lanthanum Gallate Perovskite (LaGaO3).  

E-print Network

??Pressureless-sintered lanthanum gallate (LaGaO3) ceramics have been analyzed using X-ray diffractometry (XRD), scanning electron and transmission electron microscopy (SEM and TEM), and electron-backscatter diffraction (EBSD).… (more)

Wang, Wei-Lin

2006-01-01

134

The Materials Reliability Division has established several capabilities for analyzing the reliability of  

E-print Network

for size-appropriate testing. Our capabilities include: - field emission scanning electron microscope with automated electron backscatter diffraction system (EBSD) - 200 kV transmission electron microscope - microtensile testing apparatus (custom) - contact-resonance force microscope (custom) - surface acoustic wave

135

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.

1993-01-01

136

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

NASA Astrophysics Data System (ADS)

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

Wenk, H.; Grimsich, J. L.

2012-12-01

137

Interlaboratory Comparison of Ultrasonic Backscatter Coefficient  

E-print Network

Interlaboratory Comparison of Ultrasonic Backscatter Coefficient Measurements From 2 to 9 MHz Keith coefficient is a fundamental ultrasonic property that has been used to character- ize many tissues. Unfortunately, there is currently far less standardization for the ultrasonic backscatter measurement than

Illinois at Urbana-Champaign, University of

138

Backscattering in silicon photonic waveguides and circuits  

NASA Astrophysics Data System (ADS)

The effects of roughness induced backscattering in optical waveguides and circuit realized on a silicon-on-insulator platform are investigated. A systematic experimental investigation on low-loss silicon nanowires, with a sidewall roughness rms around 1-2 nm, is presented, showing that a few hundreds of micrometers long waveguide exhibits a backscattering level that can hinder its exploitation in many applications. The effect is typically stronger for TE polarization and is significantly enhanced inside optical cavities, such as microring resonators, where backscattering is coherently enhanced according to the square of the finesse of the resonator and can modify dramatically the spectral response of the resonators, even at moderate quality factors. We found general relationships relating backscattering to the geometric and optical parameters of the waveguides, to polarization rotation effects, and to coupling with higher-order modes. On the basis of these results, design rules to mitigate backscattering effects are proposed. The main statistical properties of roughness induced backscattering were also experimentally derived, these results enabling an accurate modeling of realistic waveguides and the evaluation of the backscattering impact in integrated devices and circuits.

Morichetti, F.; Canciamilla, A.; Ferrari, C.; Martinelli, M.; Melloni, A.

2011-01-01

139

Detector for high energy photon backscatter  

SciTech Connect

High energy photon backscatter uses pair production to probe deep beneath surfaces with single side accessibility or to image thick, radiographically opaque objects. At the higher photon energies needed to penetrate thick and/or highly attenuating objects, Compton backscatter becomes strongly forward peaked with relatively little backscatter flux. Furthermore, the downward energy shift of the backscattered photon makes it more susceptible to attenuation on its outbound path. Above 1.022 MeV, pair production is possible; at about 10 MeV, pair production crosses over Compton scatter as the dominant x-ray interaction mechanism. The backscattered photons can be hard x-rays from the bremsstrahlung of the electrons and positrons or 0.511 MeV photons from the annihilation of the positron. Monte Carlo computer simulations of such a backscatter system were done to characterize the output signals and to optimize a high energy detector design. This paper touches on the physics of high energy backscatter imaging and describes at some length the detector design for tomographic and radiographic imaging.

Silver, M.D.; Erker, J.W.; Duncan, M.Z.; Hartford, T.J.; Sivers, E.A.; Hopkinson, J.F. [Bio-Imaging Research, Inc., Lincolnshire, IL (United States)

1993-12-31

140

Diffraction to De-Diffraction  

E-print Network

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

V. F. Tamari

2003-03-19

141

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

PubMed

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

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

2014-02-01

142

EBSD as a tool to identify and quantify bainite and ferrite in low-alloyed Al-TRIP steels.  

PubMed

Bainite is thought to play an important role for the chemical and mechanical stabilization of metastable austenite in low-alloyed TRIP steels. Therefore, in order to understand and improve the material properties, it is important to locate and quantify the bainitic phase. To this aim, electron backscatter diffraction-based orientation microscopy has been employed. The main difficulty herewith is to distinguish bainitic ferrite from ferrite because both have bcc crystal structure. The most important difference between them is the occurrence of transformation induced geometrically necessary dislocations in the bainitic phase. To determine the areas with larger geometrically necessary dislocation density, the following orientation microscopy maps were explored: pattern quality maps, grain reference orientation deviation maps and kernel average misorientation maps. We show that only the latter allow a reliable separation of the bainitic and ferritic phase. The kernel average misorientation threshold value that separates both constituents is determined by an algorithm that searches for the smoothness of the boundaries between them. PMID:18503676

Zaefferer, S; Romano, P; Friedel, F

2008-06-01

143

C-band backscattering from corn canopies  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

144

An energy-dependent electron backscattering coefficient  

NASA Astrophysics Data System (ADS)

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

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

1987-05-01

145

X band microwave backscattering from ocean waves  

Microsoft Academic Search

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

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

1995-01-01

146

SAR backscatter from coniferous forest gaps  

NASA Technical Reports Server (NTRS)

A study is in progress comparing Airborne Synthetic Aperture Radar (AIRSAR) backscatter from coniferous forest plots containing gaps to backscatter from adjacent gap-free plots. Issues discussed are how do gaps in the range of 400 to 1600 sq m (approximately 4-14 pixels at intermediate incidence angles) affect forest backscatter statistics and what incidence angles, wavelengths, and polarizations are most sensitive to forest gaps. In order to visualize the slant-range imaging of forest and gaps, a simple conceptual model is used. This strictly qualitative model has led us to hypothesize that forest radar returns at short wavelengths (eg., C-band) and large incidence angles (e.g., 50 deg) should be most affected by the presence of gaps, whereas returns at long wavelengths and small angles should be least affected. Preliminary analysis of 1989 AIRSAR data from forest near Mt. Shasta supports the hypothesis. Current forest backscatter models such as MIMICS and Santa Barbara Discontinuous Canopy Backscatter Model have in several cases correctly predicted backscatter from forest stands based on inputs of measured or estimated forest parameters. These models do not, however, predict within-stand SAR scene texture, or 'intrinsic scene variability' as Ulaby et al. has referred to it. For instance, the Santa Barbara model, which may be the most spatially coupled of the existing models, is not truly spatial. Tree locations within a simulated pixel are distributed according to a Poisson process, as they are in many natural forests, but tree size is unrelated to location, which is not the case in nature. Furthermore, since pixels of a simulated stand are generated independently in the Santa Barbara model, spatial processes larger than one pixel are not modeled. Using a different approach, Oliver modeled scene texture based on an hypothetical forest geometry. His simulated scenes do not agree well with SAR data, perhaps due to the simple geometric model used. Insofar as texture is the expression of biological forest processes, such as succession and disease, and physical ones, such as fire and wind-throw, it contains useful information about the forest, and has value in image interpretation and classification. Forest gaps are undoubtedly important contributors to scene variance. By studying the localized effects of gaps on forest backscatter, guided by our qualitative model, we hope to understand more clearly the manner in which spatial heterogeneities in forests produce variations in backscatter, which collectively give rise to scene texture.

Day, John L.; Davis, Frank W.

1992-01-01

147

Bathymetry and acoustic backscatter: Estero Bay, California  

USGS Publications Warehouse

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

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

2013-01-01

148

Materials Science: Diffraction  

NSDL National Science Digital Library

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

Peter Goodhew

149

Combined Raman-elastic backscatter lidar method for the measurement of backscatter ratios.  

PubMed

A variation of the conventional combined Raman-elastic backscatter lidar method, the 1-2-3 lidar method, is described and analyzed. This method adds a second transmitter wavelength to the conventional combined Raman-elastic backscatter lidar. This transmitter wavelength is identical to that of the Raman receiver. One can generate the transmitted beam at this wavelength by Raman shifting the laser radiation in molecular nitrogen or oxygen. Measuring a second elastic lidar signal at the Raman-shifted wavelength makes it possible to eliminate differential transmission effects that can cause systematic errors in conventional combined Raman-elastic backscatter lidar. PMID:18259327

Moosmüller, H; Wilkerson, T D

1997-07-20

150

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

PubMed

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

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

2013-09-01

151

Visualization of x-ray backscatter data  

SciTech Connect

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

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

1993-12-31

152

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.

1984-01-01

153

Backscattering of electrons from solid targets  

NASA Astrophysics Data System (ADS)

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

Dapor, Maurizio

1990-11-01

154

On the simulation of backscatter ionograms  

Microsoft Academic Search

An algorithm for the simulation of backscatter ionograms is developed. Propagation is evaluated by numerically ray tracing through an ionosphere consisting of Chapman layers (major layer parameters derived from CCIR and URSI maps). Simulations are performed for a variety of model ionospheres (including some with strongly varying horizontal structure such as the equatorial anomaly) and are found to reproduce many

C. J. Coleman

1997-01-01

155

Backscatter enhancement in scattering from rough surfaces  

Microsoft Academic Search

Stealth technology has advanced to the point where radar target cross sections are so small there is a great need to determine mean clutter cross sections and clutter variability with great accuracy. Established clutter prediction techniques result in forward scatter values that exceed backscatter. There is some new experimental data on light scattering from rough metallic surfaces which shows there

Robert J. Papa; Margaret B. Woodworth

1989-01-01

156

Backscattering coefficient of a perturbed sinusoidal surface  

NASA Technical Reports Server (NTRS)

A coherent model for scattering from a randomly perturbed periodic surface is developed using the Kirchhoff approximation. It is intended to model wave scattering from ground surfaces with row directions. Results are illustrated and compared with an incoherent scatter model and measured backscattering angular curves from ploughed fields.

Eom, H. J.; Fung, A. K.

1984-01-01

157

Window flaw detection by backscatter lighting  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

158

Efficient and reliable low-power backscatter networks  

E-print Network

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

Wang, Jue

159

Enabling Instantaneous Feedback with Full-duplex Backscatter  

E-print Network

to communicate directly between two low-power devices [18]. The power draw of this technique is such that both­ This paper introduces the first design that enables full- duplex communication on battery-free backscatter]: Wireless communi- cation KEYWORDS Backscatter; Full-duplex wireless; Wireless 1. INTRODUCTION Backscatter

Hochberg, Michael

160

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

E-print Network

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

161

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

SciTech Connect

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

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

2012-08-15

162

Modelling of backscatter from vegetation layers  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

163

Spectra of Particulate Backscattering in Natural Waters  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

164

Aerosol backscatter lidar calibration and data interpretation  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

165

Bomb Detection Using Backscattered X-Rays  

Microsoft Academic Search

Bomb Detection Using Backscattered X-rays*;\\u000a;\\u000aCurrently the most common method to determine the contents of a package suspected of containing an;\\u000aexplosive device is to use transmission radiography. This technique requires that an x-ray source and film;\\u000abe placed on opposite sides of the package. This poses a problem if the pachge is placed so that only one;\\u000aside

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

1998-01-01

166

Backscattering measurement from a single microdroplet.  

PubMed

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

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

2011-04-01

167

Forensic Value of Backscatter from Email Spam  

Microsoft Academic Search

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

Christopher P. Fuhrman

2008-01-01

168

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.

2009-05-01

169

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

NASA Astrophysics Data System (ADS)

The characterization of high frequency, shallow water acoustic backscatter and reverberation is important because acoustic systems are used in many scientific, commercial, and military applications. The approach taken is to use data collected by the Toroidal Volume Search Sonar (TVSS), a 68 kHz multibeam sonar capable of 360° imaging in a vertical plane perpendicular to its direction of travel. With this unique capability, acoustic backscatter imagery of the seafloor, sea surface, and horizontal and vertical planes in the volume are constructed from data obtained in 200m deep waters in the Northeastern Gulf of Mexico when the TVSS was towed 78m below the surface, 735m astern of a towship. The processed imagery provide a quasi-synoptic characterization of the spatial and temporal structure of boundary and volume acoustic backscatter and reverberation. Diffraction, element patterns, and high sidelobe levels are shown to be the most serious problems affecting cylindrical arrays such as the TVSS, and an amplitude shading method is presented for reducing the peak sidelobe levels of irregular-line and non-coplanar arrays. Errors in the towfish's attitude and motion sensor, and irregularities in the TVSS's transmitted beampattern produce artifacts in the TVSS-derived bathymetry and seafloor acoustic backscatter imagery. Correction strategies for these problems are described, which are unique in that they use environmental information extracted from both ocean boundaries. Sea surface and volume acoustic backscatter imagery are used to explore and characterize the structure of near-surface bubble clouds, schooling fish, and zooplankton. The simultaneous horizontal and vertical coverage provided by the TVSS is shown to be a primary advantage, motivating further use of multibeam sonars in these applications. Whereas boundary backscatter fluctuations are well described by Weibull, K, and Rayleigh mixture probability distributions, those corresponding to volume backscatter are multi-modal, with the log-normal distribution providing the best fits to the centers of the distributions, and the Rayleigh mixture models providing the best fits to the tails of the distributions. The largest distribution tails result from resonant microbubbles and patchy aggregations of zooplankton. The Office of Naval Research funded this work under ONR-NRL Contract No. N00014-96-1-G9I3.

Gallaudet, Timothy Cole

2001-10-01

170

Modeling strategies of ultrasound backscattering by blood  

NASA Astrophysics Data System (ADS)

Tissue characterization using ultrasound (US) scattering can allow the identification of relevant cellular biophysical information noninvasively. The characterization of the level of red blood cell (RBC) aggregation is one of the proposed applications. Different modeling strategies have been investigated by our group to better understand the mechanisms of US backscattering by blood, and to propose relevant measurable indices of aggregation. It could be hypothesized from these studies that the microstructure formed by RBC clusters is a main determinant of US backscattered power. The structure factor, which is related to the Fourier transform of the microscopic density function of RBCs, is described and used to explain the scattering behavior for different spatial arrangements of nonaggregated and aggregated RBCs. The microscopic density function was described by the Percus-Yevick approximation (nonaggregated RBCs), and for aggregated RBCs, by the Poisson distribution, the Neyman-Scott point process, and very recently by a flow-dependent rheological model. These statistical and microrheological models allowed the study of US backscattered power as a function of the hematocrit, scatterers' size, insonification frequency, and level of RBC aggregation. Experimental results available from the literature were used to validate the different approaches. [Work supported by Canadian Institutes of Health Research (MOP-36467), HSFQ, FCAR, and FRSQ.

Guy, Cloutier; David, Savery; Isabelle, Fontaine; Beng Ghee, Teh

2002-05-01

171

Backscattering from a Gaussian distributed, perfectly conducting, rough surface  

NASA Technical Reports Server (NTRS)

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

Brown, G. S.

1977-01-01

172

Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

173

[Obtaining aerosol backscattering coefficient using pure rotational Raman spectrum].  

PubMed

Atmospheric aerosol backscattering coefficient ratio can be obtained with the ratio of elastic signal to the total rotational Raman backscattering signal without assuming the ratio of aerosol extinction to backscatter. Generally, the intensity ofpartial rotational Raman spectrum lines instead of the total rotational Raman spectrum lines is measured. The intensity of the total rotational Raman spectrum lines is not dependent on the temperature, but the intensity of the partialrotational Raman spectrumlines is dependent on the temperature. So calculating aerosol backscattering coefficient ratio with the intensity of the partial rotational Raman spectrum lines would lead to an error. In the present paper, the change in the intensity sums of different rotational Raman spectrum lines with temperature was simulated and the errors of aerosol backscattering coefficient ratio derived from them were discussed. A new method was presented for measuring aerosol backscattering coefficient ratio, which needed not to measure the intensity of the total rotational Raman spectrum lines. Aerosol backscattering coefficient ratio could be obtained with the atmospheric temperature and a single rotational Raman spectrum line. Finally, a erosol backscattering coefficient ratio profiles of the atmosphere were acquired with the combined Raman lidar of our lab. The results show that there is no need to assume any relation between aerosol backscattering and extinction or to consider any wavelength calibration to determine the aerosol scattering coefficient. PMID:19123401

Su, Jia; Zhang, Yin-chao; Hu, Shun-xing; Zhao, Pei-tao; Cao, Kai-fa; Wang, Shao-lin; Xie, Jun

2008-10-01

174

Lidar Inversion of Atmospheric Backscatter and Extinction-To-Backscatter Ratios by Use of a Kalman Filter  

Microsoft Academic Search

A first inversion of the backscatter profile and extinction-to-backscatter ratio from pulsed elastic-backscatter lidar returns is treated by means of an extended Kalman filter (EKF). The EKF approach enables one to overcome the intrinsic limitations of standard straightforward nonmemory procedures such as the slope method, exponential curve fitting, and the backward inversion algorithm. Whereas those procedures are inherently not adaptable

Francesc Rocadenbosch; Cecilia Soriano; Adolfo Comerón; José-María Baldasano

1999-01-01

175

Compton backscattered collimated x-ray source  

DOEpatents

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

Ruth, R.D.; Huang, Z.

1998-10-20

176

Backscattering position detection for photonic force microscopy  

SciTech Connect

An optically trapped particle is an extremely sensitive probe for the measurement of pico- and femto-Newton forces between the particle and its environment in microscopic systems (photonic force microscopy). A typical setup comprises an optical trap, which holds the probe, and a position sensing system, which uses the scattering of a beam illuminating the probe. Usually the position is accurately determined by measuring the deflection of the forward-scattered light transmitted through the probe. However, geometrical constraints may prevent access to this side of the trap, forcing one to make use of the backscattered light instead. A theory is presented together with numerical results that describes the use of the backscattered light for position detection. With a Mie-Debye approach, we compute the total (incident plus scattered) field and follow its evolution as it is collected by the condenser lenses and projected onto the position detectors and the responses of position sensitive detectors and quadrant photodetectors to the displacement of the probe in the optical trap, both in forward and backward configurations. We find out that in the case of backward detection, for both types of detectors the displacement sensitivity can change sign as a function of the probe size and is null for some critical sizes. In addition, we study the influence of the numerical aperture of the detection system, polarization, and the cross talk between position measurements in orthogonal directions. We finally discuss how these features should be taken into account in experimental designs.

Volpe, Giovanni; Kozyreff, Gregory; Petrov, Dmitri [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain); Optique Nonlineaire Theorique, Universite Libre de Bruxelles (U.L.B.), Code Postal 231, Campus Plaine, B-1050 Bruxelles (Belgium) and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain); ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Castelldefels, Barcelona, 08860 (Spain) and ICREA--Institucio Catalana de Recerca i Estudis Avancats, Barcelona, 08010 (Spain)

2007-10-15

177

Compton backscattered collmated X-ray source  

DOEpatents

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

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

2000-01-01

178

think forward Diffraction Solutions  

E-print Network

think forward Diffraction Solutions XRD D2 PHASER Bruker AXS #12;32 Status display LEDs 1-ray diffraction? Perfect solutions for powder diffraction. And if it all fits onto a desktop, it is called D2 the whole world of powder diffraction without a lot of infrastructure. D2 PHASER ­ never before was desktop

Heller, Eric

179

Diffraction Shaders Alias wavefront  

E-print Network

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

Toronto, University of

180

Diffraction in QCD  

E-print Network

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

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

2006-04-11

181

Parabolic equation modelling of backscatter from the rough sea surface  

Microsoft Academic Search

A physically based numerical method is presented for calculating sea clutter at low grazing angles for microwave frequencies. Sea clutter is modeled as a two scale phenomenon: at low grazing angles, the backscattered energy is generated by ripples on the sea surface. A first order perturbation method gives the backscatter from a small patch of surface, as a function of

M. F. Levy

1991-01-01

182

Acoustic backscatter by schools of adult Atlantic mackerel  

Microsoft Academic Search

The extent of acoustic backscatter by schools of adult Atlantic mackerel (Scomber scombrus) is investigated to improve biomass estimates. Previous studies involving modelled scattering from individual mackerel showed that backscattering at high frequencies is dominated by the contribution from the backbone. Accurate predictions of the scattering spectra require consideration of back- scattering from the entire skeleton, including details of the

Natalia Gorska; Rolf J. Korneliussen; Egil On

183

Azimuth Variation in Microwave Backscatter over the Greenland Ice Sheet  

E-print Network

/ablation balance of the Greenland Ice Sheet is considered a sensitive indicator of global climate change. AlthoughAzimuth Variation in Microwave Backscatter over the Greenland Ice Sheet Ivan S. Ashcraft and David backscatter measurements are becoming an important tool for monitoring the dynamic behavior of the Greenland

Long, David G.

184

Depolarization of Electromagnetic Waves Backscattered from the Lunar Surface  

Microsoft Academic Search

The vector solution for the field backscattered from a random rough surface with large radii of curvature and finite conductivity is applied to radar backscatter from the moon. The resulting integrals for the cross-polarization ratio are simplified by an approximation valid for angles of incidence up to about 35 ø and are evaluated by computer simulation. The resulting curves are

Petr Beckmann

1968-01-01

185

Anomalous spectral signatures of high-intensity stimulated Raman backscattering  

Microsoft Academic Search

The nonlinear three-wave interaction model of stimulated Raman backscattering in an underdense plasma layer, with a relativistic detuning taken into account, is simulated in space-time. A mechanism is discovered based on a systematic transition to a chaotic state via quasiperiodic and intermittent regimes, that predicts a progressive growth in the backscatter complexity with an increase in laser intensity. Anomalous signatures

Milos M. Skoric; Moma S. Jovanovic; Milan R. Rajkovic

1996-01-01

186

Theory and Measurement of Backscattering from RFID Tags  

E-print Network

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

Hochberg, Michael

187

Rayleigh backscattering in a fiber gyroscope with limited coherence sources  

Microsoft Academic Search

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

W. Burns; R. Moeller

1983-01-01

188

Relating P-band AIRSAR backscatter to forest stand parameters  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

189

Surface Roughness, Optical Shadowing, and Radar Backscatter  

NASA Astrophysics Data System (ADS)

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

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

1996-03-01

190

A dynamic localization model with stochastic backscatter  

NASA Technical Reports Server (NTRS)

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

Carati, Daniele; Ghosal, Sandip

1994-01-01

191

Ocean backscatter across the Gulf Stream sea surface temperature front  

SciTech Connect

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

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

1997-06-01

192

X-Ray Diffraction.  

ERIC Educational Resources Information Center

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

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

1980-01-01

193

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

E-print Network

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

Ma, Chi

194

Diffraction Metrology and Standards  

E-print Network

Diffraction Metrology and Standards CERAMICS Our objective is the development of Standard Reference vendors supply NIST Diffraction Metrology SRMs with the equipment they sell. One vendor includes SRM 1976 the previous value. · Calibration of equipment with NIST Diffraction Metrology SRMs is requisite for ISO

Perkins, Richard A.

195

Factorisation issues in Diffraction  

E-print Network

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

196

Experimental Results on Diffraction  

E-print Network

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

197

X-ray backscatter imaging of nuclear materials  

DOEpatents

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

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

2014-09-30

198

Regression models for vegetation radar-backscattering and radiometric emission  

NASA Technical Reports Server (NTRS)

Simple regression estimation of radar backscatter and radiometric emission from vegetative terrain is proposed, based on the exact radiative transfer models. A vegetative canopy is modeled as a Rayleigh scattering layer above an irregular Kirchhoff surface. The rms errors between the exact and the estimated ones are found to be less than 5 percent for emission, and 1 dB for the backscattering case, in most practical uses. The proposed formulas are useful in quickly estimating backscattering and emission from the vegetative terrain.

Eom, H. J.

1986-01-01

199

Electromagnetic diffraction by plane reflection diffraction gratings  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

200

Orientation imaging microscopy of polycrystalline sodium chloride  

SciTech Connect

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

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

2010-04-15

201

X-Ray Backscatter Machine Support Frame  

NASA Technical Reports Server (NTRS)

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

Cannon, Brooke

2010-01-01

202

Radar backscatter modelling of forests using a macroecological approach   

E-print Network

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

Brolly, Matthew

2012-06-25

203

BASIS: A New Backscattering Spectrometer at the SNS  

SciTech Connect

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

2008-01-01

204

Cross-Imaging Platform Comparison of Ultrasonic Backscatter Coefficient  

E-print Network

Cross-Imaging Platform Comparison of Ultrasonic Backscatter Coefficient Measurements of Live Rat scanner system. Methods. Radio frequency data spanning the 1- to 14-MHz frequency range were acquired in 3

Illinois at Urbana-Champaign, University of

205

Improving ozone profile retrieval from spaceborne UV backscatter  

E-print Network

Chapter 2 Improving ozone profile retrieval from spaceborne UV backscatter spectrometers using convergence behaviour diagnostics Abstract The Ozone Profile Algorithm (OPERA), developed at KNMI, retrieves the vertical ozone distribution from nadir spectral satellite measurements of back scattered sunlight

Haak, Hein

206

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

SciTech Connect

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

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

2011-04-01

207

L-Band Radar Backscatter Modeling of Forest Stands  

Microsoft Academic Search

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

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

1987-01-01

208

An improved method of synthesizing ground backscatter ionograms for spherical ionospheres  

Microsoft Academic Search

Synthesis of ground backscatter ionograms is a useful technique for studying the structure of the ionosphere. By synthesizing backscatter ionograms from a known ionosphere, knowledge can be obtained on how variations in the ionosphere affect the shape of a backscatter ionogram. A method allowing the rapid synthesis of ground backscatter ionograms is presented. The vertical ionospheric profile is represented by

C. Y. Ong; J. A. Bennett; P. L. Dyson

1998-01-01

209

Exploring potential mechanisms responsible for observed changes of ultrasonic backscattered energy with temperature variations  

E-print Network

Exploring potential mechanisms responsible for observed changes of ultrasonic backscattered energy on probability variation of backscatter data Med. Phys. 39, 2369 (2012); 10.1118/1.3700235 Ultrasonic backscatter.1121/1.3460109 #12;Exploring potential mechanisms responsible for observed changes of ultrasonic backscattered energy

Illinois at Urbana-Champaign, University of

210

Microwave backscattering from surf zone waves  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

211

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

212

Geophysical Diffraction Tomography  

Microsoft Academic Search

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

A. J. Devaney

1984-01-01

213

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

E-print Network

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

214

Diffractive projection displays  

NASA Astrophysics Data System (ADS)

Displays based on diffraction effects can provide very high lumen output at high contrast ratio, due to the absence of polarizers, low losses, large-area light valves, and bright light sources. The electron-beam addressed oil-film diffracting light valve employed by the Eidophor is an expensive technology. Recent developments in diffraction form liquid-crystal devices, micromechanical gratings, and elastomeric deformation, could result in a low-cost high- efficiency projector. Therefore, it is of interest to examine the performance limitations of diffractive systems in general, and in relation to other systems. The throughput efficiency of a projector is related to the light source collimation required to transmit light through the limiting apertures of the system. A diffractive device expands the optical divergence, and consequently sacrifices system optical throughput. If the source collimation is increased by the availability of short-arc lamps, or laser diodes, the diffractive throughput penalty is reduced or eliminated. The performance of micromechanical and liquid-crystal diffractive structures is analyzed using a realistic arc lamp model. Theoretical limitations on projector throughput and contrast ratio are derived for diffractive systems, and compared with polarization dependent liquid crystal systems.

Armitage, David

1997-05-01

215

Diffraction Results from CDF  

SciTech Connect

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

Goulianos, Konstantin

2012-04-01

216

Optics: Laser and Diffraction  

NSDL National Science Digital Library

This site, from the University of Massachusetts at Amherst, provides a demonstration of laser light diffraction around a pinhead. Photos illustrate the demo set-up. A photo of the diffraction pattern shows Poisson's Spot, the bright spot observed in the center of the pattern.

2007-05-23

217

Surprises in aperiodic diffraction  

E-print Network

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

Michael Baake; Uwe Grimm

2009-09-30

218

Single Slit Diffraction  

NSDL National Science Digital Library

This web page includes a java illustration of single slit diffraction of light. The user can adjust the wavelength of the light and the size of the slit and observe the resultant changes in the diffraction pattern. Quantitative values for the wavelength and slit-width are given.

Kiselev, Sergey

2007-11-03

219

Experimental results on the enhanced backscatter phenomenon and its dynamics  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

220

Understanding the reverse time migration backscattering: noise or signal?  

NASA Astrophysics Data System (ADS)

Reverse time migration (RTM) backscattered events are produced by the cross-correlation between waves reflected from sharp interfaces (e.g. the top of salt bodies). Commonly, these events are seen as a drawback for the RTM method because they obstruct the image of the geologic structure. Many strategies have been developed to filter out the artifacts from the conventional image. However, these events contain information that can be used to ana- lyze kinematic synchronization between source and receiver wavefields reconstructed in the subsurface. Numeric and theoretical analysis indicate the sensitivity of the backscattered energy to velocity accuracy: an accurate velocity model maximizes the backscattered arti- facts. The analysis of RTM extended images can be used as a quality control tool and as input to velocity analysis designed to constrain salt models and sediment velocity. The analysis in this thesis suggest that we can use backscattering events along with reflection data to define a joint optimization problem for velocity model building. The gradient required for model optimization suffers from cross-talk, similar to the more conventional RTM images. In order to avoid the cross-talk, I use a directional filter based on Poynting vectors which preserves the components of the wavefield traveling in the same direction. Using backscattered waves for constraining the velocity in the sediment section requires defining the top of salt in advance, which implies a dynamic workflow for model building in salt environments where both sediment velocity and salt interface change iteratively during inversion.

Diaz Pantin, Esteban Fernando

221

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.

1991-01-01

222

Probabilities and statistics for backscatter estimates obtained by a scatterometer  

NASA Technical Reports Server (NTRS)

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

Pierson, Willard J., Jr.

1989-01-01

223

Diffraction by nanocrystals.  

PubMed

X-ray femtosecond nanocrystallography is a new, potentially powerful technique for imaging biological macromolecules that uses ensemble-averaged measurements of diffraction of x-ray free-electron laser pulses from nanocrytalline specimens. Nanocrystals have some diffraction characteristics that are distinct from those of macroscopic crystals, due to the presence of different kinds of unit cell in the crystal and of truncated unit cells on the crystal surface. Expressions are derived for diffraction by nanocrystals with variable and incomplete unit cells, averaged over a distribution of crystal sizes and shapes. The diffraction contains differently modulated Bragg components that are due to interference effects within and between the full and incomplete unit cells. Estimates are obtained for the relative magnitudes of the components. The nature of the diffraction is illustrated by two-dimensional simulations. Implications for molecular imaging are discussed. PMID:24323025

Chen, Joe P J; Millane, Rick P

2013-12-01

224

Single-Slit Diffraction  

NSDL National Science Digital Library

The Single-Slit Diffraction model simulates the diffraction pattern of light as it travels through a slit to a screen. The diffraction pattern is due to the difference in path length of the light from different parts of the slit as the light from the slit travels to the screen. The intensity of the light that reaches the screen is related to the wavelength of light, the slit width, and the angle away from the center of the screen. In the simulation one can change the wavelength, the slit separation, and whether the pattern is shown on a screen or on a photographic plate. Single-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_diffraction.jar file will run the program if Java is installed.

Palop, Jose I.

2010-12-12

225

MELT-MEDIATED LASER CRYSTALLIZATION OF THIN FILM NITI SHAPE MEMORY ALLOYS  

E-print Network

micro-structure via atomic force microscopy (AFM), electron backscatter diffraction (EBSD) and x as texture may be specifically tailored toward a range of applications. Silicon thin films have been matrix displays (e.g. LCD and OLED) as well as the active medium in thin film solar cells [4

Yao, Y. Lawrence

226

Appendixes: Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography JOHN W. VALLEY, AARON J. CAVOSIE, TAKAYUKI USHIKUBO, DAVID A. REINHARD, DANIEL F.  

E-print Network

for inside and outside of clusters from the core of zircon 01JH36-69 from Jack Hills, Western Australia the core of zircon 01JH36-69 from Jack Hills, Western Australia. Scale in nm with no vertical exaggeration backscatter diffraction (EBSD) measurement of lattice orientation of zircon 01JH36-69 from Jack Hills, Western

Carlson, Anders

227

Alternative processes for developing fabric and mineral compositional zoning in intrusive rocks  

Microsoft Academic Search

We present textural and mineral compositional analyses of samples from previously published experiments examining the behaviour of partially molten silicates in a thermal gradient and\\/or at a compositional interface. Textural and electron backscatter diffraction (EBSD) analyses demonstrate that, when new minerals grow within a temperature gradient, they develop elongation and in some cases a preferred orientation parallel to the gradient;

C. C. Lundstrom; S. Marshak; J. DeFrates; J. Mabon

2011-01-01

228

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

229

Elastic Wave Diffraction Elastic Wave Diffraction  

E-print Network

.25 - 12.5 keV #12;6 1b.2. Bragg Law1b.2. Bragg Law #12;7 2 d sin = n constructive interference diff. optics lenghts = n Bragg law W.L. Bragg geometrical optics law prediction of the angular position(r) local electron density n(r) diffraction condition )·exp()( rkr -= indVF V atomic positions periodic

del Barco, Enrique

230

Parametric Powder Diffraction  

NASA Astrophysics Data System (ADS)

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

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

231

Floc Growth and Changes in ADV Acoustic Backscatter Signal  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

232

Target reflectance measurements for calibration of lidar atmospheric backscatter data  

NASA Astrophysics Data System (ADS)

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.

1983-09-01

233

Measurement of the anisotropy factor with azimuthal light backscattering  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

234

Coherent Effects in Microwave Backscattering Models for Forest Canopies  

NASA Technical Reports Server (NTRS)

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

Saatchi, Sasan; McDonald, Kyle

1995-01-01

235

Effect of curvature on the backscattering from a leaf  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

236

Effect of curvature on the backscattering from leaves  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

237

Lidar aerosol backscatter measurements - Systematic, modeling, and calibration error considerations  

NASA Technical Reports Server (NTRS)

Sources of systematic, modeling, and calibration errors that affect the interpretation and calibration of lidar aerosol backscatter data are discussed. The treatment pertains primarily to ground-based pulsed CO2 lidars that probe the troposphere and are calibrated using hard calibration targets. However, a large part of the analysis is relevant to other types of lidar system such as lidars operating at other wavelengths; CW focused lidars; airborne or earth-orbiting lidars; lidars measuring other regions of the atmosphere; lidars measuring nonaerosol elastic or inelastic backscatter; and lidars employing other calibration techniques.

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

1985-01-01

238

Electrically tunable diffraction grating  

NASA Astrophysics Data System (ADS)

We report on electrically-driven diffraction grating, where refractive index of a liquid crystal (LC) was modulated periodically at an interval of 700 nm by applying an external DC bias to a metallic nanograting (NG). The LC-NG structure exhibited a maximum refractive index variation (?n) of 0.088 and a diffraction efficiency (?) change of 0-16% with a large diffraction angle of 64° for incident light of 633 nm wavelength. This approach, with the help of faster electronics, provides an opportunity of developing active holograms for real 3D display

Kim, Sun Il; Choi, Jun Hee; Ahn, Ho Young; Baik, Chan Wook; An, Jungkwuen; Choi, Chil-Sung; Pyun, Kyungsuk; Lee, Hong-Seok

2013-09-01

239

Multilayer dielectric diffraction gratings  

DOEpatents

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

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

1999-05-25

240

Multilayer dielectric diffraction gratings  

DOEpatents

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

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

1999-01-01

241

X-Ray Diffraction  

NSDL National Science Digital Library

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

Matter.org

242

Hard diffraction at CDF  

SciTech Connect

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

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

1996-07-01

243

Gravitational diffraction radiation  

E-print Network

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

Vitor Cardoso; Marco Cavaglia; Mario Pimenta

2006-09-13

244

Double Slit Diffraction  

NSDL National Science Digital Library

This resource illustrates the interference patterns for diffraction through double slits. A series of sources, electrons, protons, neutrons, photons, and pions, can be chosen for the virtual experiment. The energy of the source, the slit separation, and the flux rate can all be adjusted. The diffraction patterns are built from random flashes on a screen. The screens can be saved for comparison of different experiments.

Group, Kansas S.; Zollman, Dean A.

2004-03-07

245

Reflective diffraction grating  

DOEpatents

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

Lamartine, Bruce C. (Los Alamos, NM)

2003-06-24

246

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

2008-11-22

247

An Improved Monte Carlo Algorithm for Elastic Electron Backscattering  

E-print Network

An Improved Monte Carlo Algorithm for Elastic Electron Backscattering from Surfaces Ivan T. Dimov of electrons satisfies an integral equation, which might be solved by Monte Carlo methods. The Monte Carlo ap process. We introduce different weights in the Monte Carlo algorithm, which de- crease the variance. We

Dimov, Ivan

248

Microwave backscatter from the sea surface at grazing incidence  

Microsoft Academic Search

As part of the Sea Truth and Radar Systems '94 experiment on the Grand Banks of Newfoundland in December, 1994, the authors collected high resolution digital images of radar backscatter from the sea surface at low grazing angle incidence. Analysis of these images and other data collected concurrently allowed validation of certain theories of formation of the two chief components

Joseph R. Buckley; Ryan S. Johnson

1996-01-01

249

Coherent Backscattering of Ultra-cold Atoms F. Jendrzejewski,1  

E-print Network

Coherent Backscattering of Ultra-cold Atoms F. Jendrzejewski,1 K. M¨uller,1 J. Richard,1 A. Date,1) of ultra-cold atoms, in a quasi two dimensional configuration. Launching atoms with a well defined momentum of the CBS peak is studied and is found a fair agreement with predictions, at long times as well as at short

250

Noninvasive Breast Tumor Localization Based on Ultrawideband Microwave Backscatter  

E-print Network

weights and number of hidden nodes. We use CST Microwave Studio to simulate benign and malignant breastNoninvasive Breast Tumor Localization Based on Ultrawideband Microwave Backscatter Ahmad Abdul-based microwave breast imaging technique to non-invasively localize (impalpable) tumors in the breast. We consider

Bouaynaya, Nidhal

251

A relationship between ultrasonic integrated backscatter and myocardial contractile function.  

PubMed Central

We have shown previously that the physiologic, mechanical cardiac cycle is associated with a parallel, cardiac cycle-dependent variation of integrated backscatter (IB). However, the mechanisms responsible are not known. The mathematical and physiological considerations explored in the present study suggest that the relationship between backscatter and myocardial contractile function reflects cyclic alterations in myofibrillar elastic parameters, with the juxtaposition of intracellular and extracellular elastic elements that have different intrinsic acoustic impedances providing an appropriately sized scattering interface at the cellular level. Cardiac cycle-dependent changes in the degree of local acoustic impedance mismatch therefore may elicit concomitant changes in backscatter. Because acoustic impedance is determined partly by elastic modulus, changes in local elastic moduli resulting from the non-Hookian behavior of myocardial elastic elements exposed to stretch may alter the extent of impedance mismatch. When cardiac cell mechanical behavior is represented by a three-component Maxwell-type model of muscle mechanics, the systolic decrease in IB that we have observed experimentally is predicted. Our prior observations of regional intramural differences in IB and the dependence of IB on global contractile function are accounted for as well. When the model is tested experimentally by assessing its ability to predict the regional and global behavior of backscatter in response to passive left ventricular distention, good concordance is observed. Images PMID:3908482

Wickline, S A; Thomas, L J; Miller, J G; Sobel, B E; Perez, J E

1985-01-01

252

Backscatter gauge description for inspection of neutron absorber content  

NASA Astrophysics Data System (ADS)

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. A.; Gibbs, K. M.; Couture, A. H.

2013-05-01

253

Inspection of multilayer components by the neutron backscattering method  

SciTech Connect

The results of calculations and experimental examination of neutron backscattering (albedo) from multilayer components are examined. The results of calculations and experimental determination of sensitivity in thickness gauging of multilayer components are presented and the optimum conditions of inspection in the conditions with one-side access are determined.

Pekarskii, G.Sh.

1987-07-01

254

BACKSCATTER GUAGE DESCRIPTION FOR INSPECTION OF NEUTRON ABSORBER AND UNIFORMITY  

SciTech Connect

This paper describes design, calibration, and testing of a dual He-3 detector neutron backscatter gauge for use in the Savannah River Site Mixed Oxide Fuel project. The gauge is demonstrated to measure boron content and uniformity in concrete slabs used in the facility construction.

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

2012-05-23

255

Light backscattering polarization patterns from turbid media: theory and experiment  

E-print Network

of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we of the sample under investiga- tion, Hielscher et al.6,8 used a Stokes vector Mueller matrix approach

Wang, Lihong

256

New modules in the virtual backscatter lidar instrument  

Microsoft Academic Search

Since the presentation of the virtual backscatter lidar instrument in Firence, a lot of new modules have been added to the virtual instrument. A multiple hard target arrangement with selectable reflection parameters can be placed in a cloud or fog layer to simulate the collision avoidance problem. Further the complete atmospere with aerosols, molecules and clouds can be selected for

Juergen Streicher; Ines Leike; Christian Werner

2003-01-01

257

Alpha particle backscattering measurements used for chemical analysis of surfaces  

NASA Technical Reports Server (NTRS)

Alpha particle backscattering performs a chemical analysis of surfaces. The apparatus uses a curium source and a semiconductor detector to determine the energy spectrum of the particles. This in turn determines the chemical composition of the surface after calibration to known samples.

Patterson, J. H.

1967-01-01

258

Rutherford backscattering oscillation in scanning helium-ion microscopy  

SciTech Connect

Scanning helium-ion microscopy (SHIM) yields high-resolution imaging and is capable of surface elemental analysis at the nanometer scale. Here we examine recently discovered SHIM backscattered intensity oscillations versus the target atomic number. These oscillations are contrary to the expected monotonic increase of the backscattered helium-ion (He{sup +}) rate with the atomic number of elemental samples. We explore the ion-sample interaction via numerical simulations for a variety of scattering geometries and confirm the presence of oscillations. The oscillations are attributed to the atomic rather than the nuclear structure of the target. To that end, we study the link (near anticorrelation) between backscatter rate and He{sup +} beam stopping power, both versus the target atomic number. This leads us to ascribe the origin of the backscatter oscillation to the ''Z{sub 2}-oscillations'' of the stopping power in ion-beam physics, with the latter being rooted in the valence electron configuration of elemental targets.

Kostinski, Sarah; Yao, Nan [Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544 (United States)

2011-03-15

259

Theory and measurement of backscattering from RFID tags  

Microsoft Academic Search

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

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

2006-01-01

260

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

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

K. V. S. Rao

1999-01-01

261

Bathymetry and acoustic backscatter: Elwha River Delta, Washington  

USGS Publications Warehouse

The surveys were conducted using the R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping and real-time kinematic navigation equipment for accurate shallow water operations. This report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and Federal Geographic Data Committee (FGDC) metadata.

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

2011-01-01

262

Orientation dependence of broadband acoustic backscattering from live squid  

E-print Network

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

Stanton, Tim

263

Characterization of tissue microstructure using ultrasonic backscatter: Theory and technique for optimization using  

E-print Network

Characterization of tissue microstructure using ultrasonic backscatter: Theory and technique June 2002; accepted 20 June 2002 Characterization of tissue microstructure through ultrasonic of scatterers. Experimental measurements of ultrasonic backscatter from spontaneous mammary tumors in rats

Illinois at Urbana-Champaign, University of

264

Partially Coherent Backscatter in Radar Observations of Precipitation A. R. JAMESON  

E-print Network

definition, precipitation always produces incoherent scatter simply because its constituents movePartially Coherent Backscatter in Radar Observations of Precipitation A. R. JAMESON RJH Scientific considers incoherent backscatter from precipitation. Can precipitation generate coherent scatter as well

Kostinski, Alex

265

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

2011-12-01

266

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

267

A comparative study of RADAR Ka-band backscatter  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

268

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

E-print Network

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

Paris-Sud XI, Université de

269

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

E-print Network

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

New Hampshire, University of

270

Sensitivity of the backscattering Mueller matrix to particle shape and thermodynamic phase  

E-print Network

Sensitivity of the backscattering Mueller matrix to particle shape and thermodynamic phase Ping The Mueller matrix M corresponding to the phase matrix in the backscattering region scattering angles ranging, compact columns, and columns . It is shown that the contour patterns of the backscattering Mueller matrix

Baum, Bryan A.

271

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

NASA Technical Reports Server (NTRS)

Aerosol concentrations and size distributions in the middle and upper troposphere over the remote Pacific Ocean were measured with a forward scattering spectrometer probe (FSSP) on the NASA DC-8 aircraft during NASA's Global Backscatter Experiment (GLOBE) in May-June 1990. The FSSP size channels were recalibrated based on refractive index estimates from flight-level aerosol volatility measurements with a collocated laser optical particle counter (LOPC). The recalibrated FSSP size distributions were averaged over 100-s intervals, fitted with lo-normal distributions and used to calculate aerosol backscatter coefficients at selected wavelengths. The FSSP-derived backscatter estimates were averaged over 300-s intervals to reduce large random fluctuations. The smoothed FSSP aerosol backscatter coefficients were then compared with LOPC-derived backscatter values and with backscatter measured at or near flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.25, and 10.59 micrometers. Agreement between FSSP-derived and lidar-measured backscatter was generally best at flight level in homogeneous aerosol fields and at high backscatter values. FSSP data often underestimated low backscatter values especially at the longer wavelengths due to poor counting statistics for larger particles (greater than 0.8 micrometers diameter) that usually dominate aerosol backscatter at these wavelengths. FSSP data also underestimated backscatter at shorter wavelengths when particles smaller than the FSSP lower cutoff diameter (0.35 micrometers) made significant contributions to the total backscatter.

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

1996-01-01

272

Knife Edge Diffraction Signal attenuation caused by diffraction of waves  

E-print Network

Knife Edge Diffraction · Signal attenuation caused by diffraction of waves ­ Huygen's principle E E d i i d : Diffraction loss due to the presence of knife-edge wrt free space LOS E-field #12 The diffraction loss due to the presence of a knife edge, as compared to the free space E-field can be given

Cetiner, Bedri A.

273

Three-dimensional Quantum Slit Diffraction and Diffraction in Time.  

E-print Network

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

Paris-Sud XI, Université de

274

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.

1996-01-01

275

Diffractive dijet production  

NASA Astrophysics Data System (ADS)

We explore the diffractive interaction of a proton with an antiproton which results in centrally produced dijets. This process has been recently studied at the Tevatron. We make predictions within an Ingelman-Schlein approach and compare them to the recent data presented by the CDF Collaboration. Earlier calculations resulted in theoretical cross-sections which are much larger than those observed by CDF. We find that, after consideration of hadronisation effects and the parton shower, and using parton density functions extracted from diffractive deep inelastic scattering at HERA, it is possible to explain the CDF data. We need to assume a gap survival probability of around 10% and this is in good agreement with the value predicted by theory. We also find that the non-diffractive contribution to the process is probably significant in the kinematical region probed by the Tevatron.

Appleby, R. B.; Forshaw, J. R.

2002-08-01

276

White light conical diffraction.  

PubMed

Conical diffraction occurs when light is incident along the optic axis of a biaxial crystal. The light spreads out into a hollow cone inside the crystal, emerging as a hollow cylinder. The intensity distribution beyond the crystal is described using an adapted paraxial wave dispersion model. We show, experimentally and theoretically, how this results in a transition from conical diffraction for wavelengths at which the crystal is aligned to double refraction for misaligned wavelengths when using a white light source. The radius of the ring and location of the focal image plane (FIP) are also observed to have a wavelength dependency. The evolution of the conically diffracted beam beyond the FIP into the far field is studied and successfully described using a theoretical model. PMID:24105584

Darcy, R T; McCloskey, D; Ballantine, K E; Jennings, B D; Lunney, J G; Eastham, P R; Donegan, J F

2013-08-26

277

Diffraction Shaders Jos Stam \\Lambda  

E-print Network

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

Toronto, University of

278

Interference and Diffraction  

NSDL National Science Digital Library

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

2012-05-30

279

DIFFRACTION FROM MODEL CRYSTALS  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

280

Motives from Diffraction  

E-print Network

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

Jan Stienstra

2005-11-19

281

X-ray Diffraction  

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

2012-03-08

282

Fresnel Diffraction Applet  

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

2004-07-13

283

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

NASA Technical Reports Server (NTRS)

During NASA's GLObal Backscatter Experiment (GLOBE) II flight mission over the Pacific Ocean in May-June 1990, extensive aerosol backscatter data sets from two continuous wave, focused CO2 Doppler lidars and an aerosol microphysics data set from a laser optical particle counter (LOPC) were obtained. Changes in aerosol loading in various air masses with associated changes in chemical composition, from sulfuric acid and sulfates to dustlike crustal material, significantly affected aerosol backscatter, causing variation of about 3 to 4 orders of magnitude. Some of the significant backscatter features encountered in different air masses were the low backscatter in subtropical air with even lower values in the tropics near the Intertropical Convergence Zone (ITCZ), highly variable backscatter in the ITCZ, mid-tropospheric aerosol backscatter background mode, and high backscatter in an Asian dust plume off the Japanese coast. Differences in aerosol composition and backscatter for northern and southern hemisphere also were observed. Using the LOPC measurements of physical and chemical aerosol properties, we determined the complex refractive index from three different aerosol mixture models to calculate backscatter. These values provided a well-defined envelope of modeled backscatter for various atmospheric conditions, giving good agreement with the lidar data over a horizontal sampling of approximately 18000 km in the mid-troposphere.

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

1997-01-01

284

Parabolic equation modelling of backscatter from the rough sea surface  

NASA Astrophysics Data System (ADS)

A physically based numerical method is presented for calculating sea clutter at low grazing angles for microwave frequencies. Sea clutter is modeled as a two scale phenomenon: at low grazing angles, the backscattered energy is generated by ripples on the sea surface. A first order perturbation method gives the backscatter from a small patch of surface, as a function of the angle of incidence and of the magnitude of the incident field. Returns from a clutter cell are obtained by incoherent summation of these echoes. Shadowing and tilting effects due to the larger scale components of the sea surface are modeled using a finite difference implementation of the parabolic equation method, which also deals with atmospheric refraction effects. Realizations of the sea surface with the desired spectral characteristics are generated with a Monte Carlo method. Results are presented at S band and X band for a variety of propagation conditions.

Levy, M. F.

1991-09-01

285

Backscatter, filamentation and laser light smoothing in flowing plasmas.  

NASA Astrophysics Data System (ADS)

The three-dimensional (3-D) code F3D with nonlinear hydrodynamics (C. H. Still et al., BAPS 40), 1823 (1995). is used to examine filamentation and backscatter driven by non-uniform laser beams. Previous work with linearized hydrodynamics demonstrated that both supersonic and subsonic transverse flow deflects the laser beam in the flow direction. (D. E. Hinkel et al., accepted, PRL, June, 1996.) In agreement with analytic estimates, (D. E. Hinkel and E. A. Williams, BAPS 37), 1376 (1992). 3-D simulations of uniform, initially stationary plasma show that laser beam RPP hotspots move, yielding a time averaged laser intensity smoother than the instantaneous pattern. This naturally occurring smoothing will be compared to that in two-dimensional simulations. (A. J. Schmitt and B. B. Afeyan, BAPS 40). 1824 (1995). The influence of 3-D beam structure on filamentation, Brillouin backscatter and beam smoothing will be examined with and without axial and transverse flow.

Hinkel, D. E.; Still, C. H.; Berger, R. L.; Langdon, A. B.; Williams, E. A.

1996-11-01

286

Airborne backscatter lidar measurements at three wavelengths during ELITE  

NASA Astrophysics Data System (ADS)

The German Aerospace Establishment (DLR) operates an airborne backscatter lidar based on a Nh:YAG laser which is flashlamp-pumped at 10 Hz. It works on the wavelengths 1064, 532, and 354 nm. It is mounted downward-looking on the research aircraft Falcon 20, flying at about 12 km altitude at speeds of 200 m/s. We present airborne measurements correlated with the orbit tracks of the shuttle-borne LITE-instrument (lidar in-space technology experiment). The emphasis in data evalution is on the comparison between the airborne and the shuttle- borne lidars. First results show excellent agreement between the two instruments even on details of cirrus clouds. The results comprise cloud geometrical and optical depths, as well as profiles of aerosol backscattering coefficients at three wavelengths.

Schreiber, H. G.; Wirth, Martin; Moerl, P.; Renger, Wolfgang

1995-09-01

287

Investigation of binary compounds using electron Rutherford backscattering  

SciTech Connect

High-energy (40 keV) electrons, scattering over large angles, transfer a small fraction of their kinetic energy to the target atoms, in the same way as ions do in Rutherford backscattering experiments. The authors show here that this energy transfer can be resolved and used to determine the mass of the scattering atom. In this way information on the surface composition for thicknesses of the order of 10 nm can be obtained. The authors refer to this technique as 'electron Rutherford backscattering'. In addition the peak width reveals unique information about the vibrational properties (mean kinetic energy) of the scattering atoms. Here the authors demonstrate that the method can be used to identify a number of technologically important compounds.

Went, M. R.; Vos, M. [Atomic and Molecular Physics Laboratories, Research School of Physical Sciences and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

2007-02-12

288

Sensor of back-scattered light polarization in body cells  

NASA Astrophysics Data System (ADS)

The biological tissues consist of cells which dimensions are bigger than a wavelength of visible light. Therefore a Mie scattering of transmitted and reflected light occurs and different polarization states arise. The back-scattered polarized laser light exhibits multiple scattering from the surface and subsurface layers of the sample. Notwithstanding this phenomenon is different if the cellular tissues are live or dead. In the case of porcine meat, there are temporal and dynamic changes not only as a result of chemical process, but also geometric deformations due to the water evaporation from intracellular and extracellular sites. Although multiple scattering in tissue randomizes incident polarization states, the shift of polarization can be clearly observed in diffusive scattering pattern due to the muscle orientation and meat aging. Accordingly, these temporal changes due to the multiple scattering of backscattered light allow measure the freshness of processed meat.

Tománek, Pavel; Mikláš, Jan; Bajgar, Aleš; Grmela, Lubomír; Dobis, Pavel; Brüstlová, Jitka

2009-05-01

289

RFID tag modification for full depth backscatter modulation  

SciTech Connect

A modulated backscatter radio frequency identification device includes a diode detector configured to selectively modulate a reply signal onto an incoming continuous wave; communications circuitry configured to provide a modulation control signal to the diode detector, the diode detector being configured to modulate the reply signal in response to be modulation control signal; and circuitry configured to increase impedance change at the diode detector which would otherwise not occur because the diode detector rectifies the incoming continuous wave while modulating the reply signal, whereby reducing the rectified signal increases modulation depth by removing the reverse bias effects on impedance changes. Methods of improving depth of modulation in a modulated backscatter radio frequency identification device are also provided.

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

2010-07-20

290

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

USGS Publications Warehouse

In the summer of 2008, as part of the California Seafloor Mapping Program (CSMP) the U.S. Geological Survey, Coastal and Marine Geology mapped a nearshore region of the northern Santa Barbara Channel in Southern California (fig 1). The CSMP is a cooperative partnership between Federal and State agencies, Universities, and Industry to create a comprehensive coastal/marine geologic and habitat basemap series to support the Marine Life Protection Act (MLPA) inititive. The program is supported by the California Ocean Protection Council and the California Coastal Conservancy. The 2008 mapping collected high resolution bathymetry and acoustic backscatter data using a bathymetric side scan system within State waters from about the 10-m isobath out over 3-nautical miles. This Open-File Report provides these data in a number of different formats, as well as a summary of the mapping mission, maps of bathymetry and backscatter, and FGDC metadata.

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

2010-01-01

291

Lidar extinction-to-backscatter ratio of the ocean.  

PubMed

Bio-optical models are used to develop a model of the lidar extinction-to-backscatter ratio applicable to oceanographic lidar. The model is based on chlorophyll concentration, and is expected to be valid for Case 1 waters. The limiting cases of narrow- and wide-beam lidars are presented and compared with estimates based on in situ optical measurements. Lidar measurements are also compared with the model using in situ or satellite estimates of chlorophyll concentration. A modified lidar ratio is defined, in which the properties of pure sea water are removed. This modified ratio is shown to be nearly constant for wide-beam lidar operating in low-chlorophyll waters, so accurate inversion to derive extinction and backscattering is possible under these conditions. This ratio can also be used for lidar calibration. PMID:25089487

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

2014-07-28

292

Camera for recording light backscattered from textured photovoltaic samples  

NASA Astrophysics Data System (ADS)

A camera for recording the intensity of light backscattered from textured photovoltaic (PV) samples is described. It was realized by modifying a professional folding camera, for use on an optical bench. The collimated light from a laser source crosses the camera and impinges on the test sample. The light backscattered by the sample exposes a punched photographic plate placed on the front side of the camera. With a proper choice of laser light intensity and wavelength, the optical diffusing effects produced by surface morphology or by subsurface features of the sample can be recorded in this way. The analysis of light diffusing characteristics of textured PV samples, mainly based on crystalline silicon material, can be directed towards improving their light collection capabilities. The camera can be assembled in such a way as to record the light diffusion images produced in reflection by both small and large samples, or those produced in transmission from textured semitransparent materials.

Parretta, Antonio

2003-09-01

293

How to suppress the backscattering of conduction electrons?  

NASA Astrophysics Data System (ADS)

It is shown theoretically that the strong coupling of electrons to a high-frequency electromagnetic field results in the nulling of electron backscattering within the Born approximation. The conditions of the effect depend only on field parameters and do not depend on the concrete form of the scattering potential. As a consequence, this phenomenon is of universal physical nature and can take place in various conducting systems. Since the suppression of electron backscattering results in decreasing electrical resistance, the solved quantum-mechanical problem opens a new way to control electronic transport properties of conductors by a laser-generated field. Particularly, the elaborated theory is applicable to nanostructures exposed to a strong monochromatic electromagnetic wave.

Kibis, O. V.

2014-09-01

294

Calculations of radar backscattering coefficient of vegetation-covered soils  

NASA Technical Reports Server (NTRS)

The present investigation has the objective to develop a simple 'user's' model for simulating the measured radar backscattering coefficients from vegetation-covered fields in conjunction with the data obtained by Jackson et al. (1980, 1982). The theoretical work reported by Fung and Eom (1981) provides the basis for the model. Certain modifications are related to a consideration of the effect of a vegetation canopy. The first part of the model is concerned with a description of scatter from rough bare soil, while the second part takes into account the effect of a vegetation cover. It is shown that the measured angular distribution of the backscattering coefficient of vegetation-covered fields can be satisfactory reproduced by using the developed model.

Mo, T.; Schmugge, T. J.; Jackson, T. J.

1984-01-01

295

Tunable backscattering in quantum Hall systems induced by neighbouring gates  

NASA Astrophysics Data System (ADS)

Using focussed ion beam writing we define an in-plane gate (IPG) modified with a bay. Biasing this IPG modifies on the one hand the edge potential and on the other hand the bay width. The first effect governs the interchannel scattering, the second one the backscattering in general. We measure the longitudinal resistance Rxx( B) for different gate voltages VGate. In the quantum regime both effects are responsible for an increased dependence of the Rxx( x)-peaks and especially of the neighbouring spin-split maxima ratio on VGate compared to a simple IPG. A structure with a longer slit realized with two neighbouring IPGs is used to examine the backscattering in the bay region.

Heidtkamp, C.; Meier, C.; Reuter, D.; Versen, M.; Hoch, S.; Diaconescu, D.; Wieck, A. D.

2000-07-01

296

Coherent inelastic backscattering of laser light from three isotropic atoms  

NASA Astrophysics Data System (ADS)

We study the impact of double- and triple-scattering contributions on coherent backscattering of laser light from saturated isotropic atoms in the helicity-preserving polarization channel. By using the recently proposed diagrammatic pump-probe approach, we analytically derive single-atom spectral responses to a classical polychromatic driving field, combine them self-consistently to double- and triple-scattering processes, and numerically deduce the corresponding elastic and inelastic spectra, as well as the total backscattered intensities. We find that accounting for the triple-scattering contribution leads to a faster decay of phase-coherence with increasing saturation of the atomic transition as compared with double scattering alone and to a better agreement with the experiment on strontium atoms.

Ketterer, Andreas; Buchleitner, Andreas; Shatokhin, Vyacheslav N.

2014-11-01

297

Observation of transverse coherent backscattering in disordered photonic structures  

E-print Network

We report on the experimental observation of weak localization in an optically induced disordered (2+1)-dimensional photonic structure. Our flexible method of optical induction is applied with a nondiffracting random intensity distribution. We focus on the analysis of a statistical output spectrum for many probe events with variance of the incoming beam's transverse spatial frequency. For particular spatial frequencies we find considerable signatures of transverse coherent backscattering.

Brake, Sebastian; Leykam, Daniel; Desyatnikov, Anton; Denz, Cornelia

2015-01-01

298

Dependence of radar backscatter on coniferous forest biomass  

Microsoft Academic Search

Two independent experimental efforts have examined the dependence of radar backscatter on above-ground biomass of monospecie conifer forests using polarimetric airborne SAR data at P-, L- and C-bands. Plantations of maritime pines near Landes, France, range in age from 8 to 46 years with above-ground biomass between 5 and 105 tons\\/ha. Loblolly pine stands established on abandoned agricultural fields near

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

1992-01-01

299

Method and apparatus for measuring lung density by Compton backscattering  

DOEpatents

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

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

1988-03-11

300

Measurement of magnetic field using Rayleigh backscattering in optical fibres  

SciTech Connect

In this paper, we investigate the use of optical reflectometry in optical fibres for the measurement of magnetic field. The dedicated application concerns the measurement of plasma current in the fusion reactor. The measurement is based on the rotation of the polarization state of the Rayleigh backscattered signal when an optical pulse is launched in the fibre. Particular care has been undertaken to evaluate the impact of linear birefringence on the measurement performance. (authors)

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

2011-07-01

301

Method and apparatus for measuring lung density by Compton backscattering  

DOEpatents

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

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

1991-01-01

302

Damage in silicon carbide induced by Rutherford backscattering analysis  

Microsoft Academic Search

Damage in silicon carbide generated by ion implantation or irradiation is usually analyzed by Rutherford backscattering spectroscopy in combination with channeling (RBS\\/C) of MeV He+ ions, a technique which is considered to be largely non-destructive. In this paper we report on swelling of 6H–SiC induced by He+ implantation at doses commensurate with, or lower than those commonly used for obtaining

W. Fukarek; R. A Yankov; W. Anwand; V. Heera

1998-01-01

303

Backscattering from capillary waves with application to sea clutter  

Microsoft Academic Search

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

J. Wright

1966-01-01

304

Intraluminal ultrasound intensity distribution and backscattered Doppler power.  

PubMed

Ultrasound (US) incident obliquely on a cylindrical vessel is redistributed in space when the propagation path includes walls with acoustic impedance different from that of the surrounding media. We investigated this using low-density polyethylene (PE) as the vessel wall material. Both simulations and experiments were carried out. Direct hydrophone measurements of the acoustic field were made within a half section of the PE tube, and the distribution of backscattered Doppler power along a scan line was obtained using a range-Doppler instrument. Both simulation and hydrophone results demonstrate lateral shadow regions within the lumen. In every one of various Doppler flow experiments conducted, the backscattered Doppler power, compensated for on-axis transducer behaviour, increased with depth. Simulation results for an incident continuous-wave (CW) plane wave show that it tends to be focused by the curvature of the PE tube walls. The wall interactions are, however, angle-dependent and so the behaviour of a focused US beam depends on the beam as well as the walls. This study demonstrates alterations in the spatial distribution of US within a cylindrical vessel as a result of known vessel wall properties. It also provides evidence that local intensity variations within the lumen affect the relative Doppler power backscattered from small sample volumes. PMID:15588959

Thompson, Rosemary S; Bambi, Giacomo; Steel, Robin; Tortoli, Piero

2004-11-01

305

Measuring Ultrasonic Backscatter in the Presence of Nonlinear Propagation  

NASA Astrophysics Data System (ADS)

A goal of medical ultrasound is the formation of quantitative ultrasound images in which contrast is determined by acoustic or physical properties of tissue rather than relative echo amplitude. Such images could greatly enhance early detection of many diseases, including breast cancer and liver cirrhosis. Accurate determination of the ultrasonic backscatter coefficient from patients remains a difficult task. One reason for this difficulty is the inherent nonlinear propagation of ultrasound at high intensities used for medical imaging. The backscatter coefficient from several tissue-mimicking samples were measured using the planar reflector method. In this method, the power spectrum from a sample is compared to the power spectrum of an optically flat sample of quartz. The results should be independent of incident pressure amplitude. Results demonstrate that backscatter coefficients can vary by more than an order of magnitude when ultrasound pressure varies from 0.1 MPa to 1.5 MPa at 5.0 MHz. A new method that incorporates nonlinear propagation is proposed to explain these discrepancies.

Stiles, Timothy; Guerrero, Quinton

2011-11-01

306

Experimental findings in 180{degree} backscattering enhancement from solids  

SciTech Connect

We use a backscattering assembly developed recently to investigate the enhanced backscattering from polycrystalline materials near 180{degree}. The nominal scattering angle can be continuously varied between exactly 180.0{degree} and 178.5{degree}. It is shown that the stochastic model of flux peaking, though its predictions are surprisingly consistent with experimental results, either does not apply to real measurements or does only take account of a negligible fraction of the effect, which cannot be documented by experiment. The energy loss of He projectiles along correlated inward and outward trajectories turns out to be the same as in any random direction. To get the enhancement factor unaffected from detector resolution we measured the integrated backscattering yield from a number of targets with different thickness and deduced the yield by two different methods. For 400 keV He projectiles scattered from partly oxidized Ta a maximum enhancement factor of 2.8 is found. {copyright} {ital 1997} {ital The American Physical Society}

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

1997-02-01

307

Production Processing of Multibeam Backscatter Data for Sediment Characterization  

E-print Network

Over the past decade, multibeam echo sounders have become accepted as standard hydrographic tools. As with single-beam sounder data, there is more information in the echo than just water depth. Quester Tangent Corporation has developed a technique to apply statistical signal processing techniques to multibeam sonar data to classify the seabed. The approach classifies backscatter imagery by dividing the raw image data into rectangular patches, generating feature values based on the statistics of the backscatter in each, finding the principal components of the set of feature vectors, and identifying clusters having a similar acoustic response. A catalogue of bottom types can then be produced and applied to any data set provided the multibeam system was operated in a consistent way. When plotted on a map, the results show the seabed’s acoustic diversity. Of primary importance in the objective classification of multibeam sonar is compensating the image for changes in backscatter with grazing angle and range, and quality control on the bottom pick. Of similar importance is the speed and ease at which the significant volumes of multibeam data can be processed. By integrating the classification process performed in QTC MULTIVIEW with the multibeam bathymetric data and geomatics capability of Caris, cost effective production of seabed classification data can be achieved. Examples of results from various surveys are presented along with time budgets for data processing.

unknown authors

308

Visibility related to backscatter at 1.54 micron  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

309

Inspection of reinforced concrete samples by Compton backscattering technique  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

310

Diffraction in ep collisions Pierre Van Mechelen  

E-print Network

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

311

Lidar inversion of atmospheric backscatter and extinction-to-backscatter ratios by use of a Kalman filter.  

PubMed

A first inversion of the backscatter profile and extinction-to-backscatter ratio from pulsed elastic-backscatter lidar returns is treated by means of an extended Kalman filter (EKF). The EKF approach enables one to overcome the intrinsic limitations of standard straightforward nonmemory procedures such as the slope method, exponential curve fitting, and the backward inversion algorithm. Whereas those procedures are inherently not adaptable because independent inversions are performed for each return signal and neither the statistics of the signals nor a priori uncertainties (e.g., boundary calibrations) are taken into account, in the case of the Kalman filter the filter updates itself because it is weighted by the imbalance between the a priori estimates of the optical parameters (i.e., past inversions) and the new estimates based on a minimum-variance criterion, as long as there are different lidar returns. Calibration errors and initialization uncertainties can be assimilated also. The study begins with the formulation of the inversion problem and an appropriate atmospheric stochastic model. Based on extensive simulation and realistic conditions, it is shown that the EKF approach enables one to retrieve the optical parameters as time-range-dependent functions and hence to track the atmospheric evolution; the performance of this approach is limited only by the quality and availability of the a priori information and the accuracy of the atmospheric model used. The study ends with an encouraging practical inversion of a live scene measured at the Nd:YAG elastic-backscatter lidar station at our premises at the Polytechnic University of Catalonia, Barcelona. PMID:18319906

Rocadenbosch, F; Soriano, C; Comerón, A; Baldasano, J M

1999-05-20

312

Towards understanding the nature of high frequency backscatter from cells and tissues: an investigation of backscatter power spectra from different concentrations of cells of different sizes  

Microsoft Academic Search

During cell death, a series of structural changes occur within the cell. We have shown that cell ensembles and tissues undergoing structural changes associated with various cell death pathways can be detected using high-frequency ultrasound. In our effort to understand better the nature of backscatter from collections of cells (which emulate tissues), we have collected raw RF backscatter data from

Michael C Kolios; G. J. Czarnota; A. Worthington; A. Giles; A. S. Tunis; M. D. Sherar

2004-01-01

313

SINGLE CRYSTAL NEUTRON DIFFRACTION.  

SciTech Connect

Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

KOETZLE,T.F.

2001-03-13

314

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.

315

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.

2007-12-27

316

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

317

Optical backscattering in the Arabian Sea—continuous 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

2001-11-01

318

Improved Standards in Laser Diffraction  

Microsoft Academic Search

Since the introduction of laser diffraction for particle size analysis in the beginning of the 1970's the verification of the complete laser diffraction system is a challenge. The first paper titled \\

Wolfgang Witt; Thomas Stübinger; Jens Jordan

2008-01-01

319

Diffraction of a Laser Beam.  

ERIC Educational Resources Information Center

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

Jodoin, Ronald E.

1979-01-01

320

QCD Aspects of Hadronic Diffraction  

NASA Astrophysics Data System (ADS)

Experimental results on soft and hard diffractive processes obtained by the CDF Collaboration in bar {p} p interactions are examined with emphasis on regularities that point to QCD aspects of hadronic diffraction. Data are interpreted in a phenomenological approach in which diffractive cross sections are related to the underlying inclusive parton distribution functions of the nucleon. In this approach, diffraction appears to be mediated by the exchange of low-x partons subject to color constraints.

Goulianos, Konstantin

321

Diffraction-Based Optical Switch  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

322

Diffractive Physics Results at CDF  

NASA Astrophysics Data System (ADS)

Forward detectors are described together with the first physics results from Run II. Using new data and dedicated diffractive triggers, a measurement of single diffractive dijet production rate, with particular focus on the diffractive structure function of the antiproton, is discussed. Upper limits on the exclusive dijet and ? 0c production cross sections are also presented.

Gallinaro, M.

2004-01-01

323

Diffraction at HERA Vitaliy Dodonov  

E-print Network

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

324

Molecular Expressions: Diffraction of Light  

NSDL National Science Digital Library

This item is an introductory tutorial on the topic of diffraction of light waves. It explains the phenomenon in a variety of ways and provides real-life examples of diffraction patterns. Related interactive simulations demonstrate basic properties of light being diffracted through a slit and allow users to explore more complex phenomena such as Airy disk patterns.

Davidson, Michael

2009-05-26

325

Accuracy in Powder Diffraction IV  

E-print Network

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

Magee, Joseph W.

326

DIFFRACTION BY EDGES ANDRAS VASY  

E-print Network

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

Vasy, András

327

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.

2014-04-01

328

Trajectory reversal approach for electron backscattering from solid surfaces  

NASA Astrophysics Data System (ADS)

The backscattering of medium energy electrons from solid surfaces is investigated by analysis of a linearized Boltzmann-type kinetic equation. A closed expression is derived for the Green’s function in an infinite medium valid for a spherically symmetric potential describing the interaction with the ionic subsystem. The solution is expressed in terms of fluctuations of the energy loss and scattering angles and the collision statistics associated with them. Since the fluctuation part is independent of the boundary conditions of the considered problem, solution of the backscattering problem requires an appropriate treatment of the collision statistics. In this context, the exact solution for the Oswald-Kasper-Gaukler model is derived and its limitations are analyzed. An exact approach is presented and implemented in an efficient Monte Carlo scheme based on the trajectory reversal technique. The resulting procedure is faster than the conventional Monte Carlo algorithm by several orders of magnitude. Results for the angular distribution are compared with conventional Monte Carlo calculations and perfectly agree with the latter within their statistical uncertainty. A second approximate algorithm is also given. The approximation involved in this second procedure turns out to be very reasonable: deviations from direct Monte Carlo calculations remain below ˜5% for energies exceeding 200eV . The integral elastic-backscattering coefficient for normal incidence for a large number of materials in the energy range 50eV-10keV is found to approximately exhibit a universal dependence on the ratio of the inelastic and the transport mean free paths, the so-called scattering parameter.

Werner, Wolfgang S. M.

2005-03-01

329

Optical properties of the scales of Morpho rhetenor butterflies: theoretical and experimental investigation of the back-scattering of light in the visible spectrum.  

PubMed Central

A study of the optical properties of the largely periodic microstructure occurring on the wings of the iridescent tropical butterfly Morpho rhetenor and responsible for its structural colouration is reported. An extensive measurement of the back-scattering of visible light from butterfly scales was performed for various angles of incidence. Efficient low-pass filter behaviour was observed for all angles of incidence and polarizations, with near-complete transmission at wavelengths above the threshold of 550 nm. The angular spread of the back-scattered light was found to be organized in lobes with total extinction of the specular reflection for all conditions of incidence. Retro-reflector behaviour was also observed for angles of incidence of 30 degrees and above. Additionally, the role of periodic geometrical features found in the microstructure for the generation of its spectral response was analysed theoretically. Using finite-difference time-domain and near-field to far-field transformation techniques, the back-scattering of visible light by models was computed numerically and the relevance of geometrical features for the production of structural colour and diffraction was demonstrated. PMID:16849152

Plattner, L.

2004-01-01

330

Spectroscopic diffraction phase microscopy.  

PubMed

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

2012-08-15

331

Relating the microwave backscattering coefficient to leaf area index  

NASA Technical Reports Server (NTRS)

This paper examines the relationship between the microwave backscattering coefficient of a vegetation canopy, sigma (can, 0) and the canopy's leaf area index (LAI). The relationship is established through the development of one model for corn and sorghum and another for wheat. Both models are extensions of the cloud model of Attema and Ulaby (1978). Analysis of experimental data measured at 8.6, 13.0, 17.0, and 35.6 GHz indicates that most of the temporal variations of sigma (can, 0) can be accounted for through variations in green LAI alone, if the latter is greater than 0.5.

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

1984-01-01

332

Ozone profiling from backscattered UV radiance measurements: a new procedure.  

PubMed

This paper presents a data analysis technique that has been developed to support a stratospheric ozone measurement and profiling program. The data consist of solar backscattered UV radiation monitored by a spacecraft. The output consists of ozone mixing ratio profiles complete with error bars throughout the atmosphere. The technique is based upon principles of nonlinear optimal estimation. It provides a number of desirable features that have not been available together in any previously constructed technique for the problem. Iteration on both radiation measurements and total ozone measurements is among these features. PMID:20309235

Whitney, C K; Malchow, H L; Cunnold, D M

1981-03-15

333

Low-Frequency Electromagnetic Backscatter from Buried Tunnels  

SciTech Connect

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

Casey, K; Pao, H

2006-06-21

334

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.

2011-01-01

335

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.

2013-08-01

336

The effect of large-scale ionospheric gradients on backscatter ionograms  

Microsoft Academic Search

This paper presents the results of the synthesis of a range of backscatter ionograms using ray tracing through model ionospheres. The backscatter ionograms were obtained by the Jindalee over-the-horizon radar facility at Alice Springs in northern Australia. Sample ionograms obtained during 1990 were used, and the study concentrated on reproducing effects due to sunrise-sunset gradients and the equatorial anomaly. Backscatter

C. J. Russell; P. L. Dyson; Z. Houminer; J. A. Bennett; L. Li

1997-01-01

337

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

SciTech Connect

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)

2013-08-28

338

Powder Diffraction in Zeolite Science  

NASA Astrophysics Data System (ADS)

This tutorial discusses the fundamental principles of X-ray diffraction and its applications in zeolite science. The early sections review the physics of diffraction, crystal symmetry, and reciprocal space. We discuss how the intensity of diffracted radiation is affected both by geometric effects involving detection (the Lorentz-polarization factor) and by the arrangement of atoms within the crystal (the structure factor). The differences between powder diffraction and single-crystal diffraction are then described, and differences between X-ray and neutron diffraction are also discussed. Later sections describe the effects of symmetry, lattice substitution, crystallite size, residual strain, preferred orientation, and X-ray absorption. Special emphasis is placed on the proper application of the Scherrer analysis in reporting crystalize size. The principles of structure solution from direct methods and Patterson methods are then introduced, and a description of Rietveld analysis is given. Finally the effects of stacking disorder on a powder diffraction pattern are presented.

Burton, Allen W.

339

Effects of macrofauna on acoustic backscatter from the seabed: Field manipulations in West Sound, Orcas Island,  

E-print Network

backscatter from patches of the small protobranch bivalve Acila castrensis, and of the cockle Clinocardium latifrons), burrowing sea cucumbers (Molpadia intermedia), crabs (Cancer magister), large cockles

Jumars, Pete

340

Effects of soil and canopy characteristics on microwave backscattering of vegetation  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

341

Diffraction Gratings WDM Components  

NASA Astrophysics Data System (ADS)

Diffraction grating WDM components have tremendous capability in number of channels (160 channel components and more with bi-directionality are commercially available and components with two times more channels have been demonstrated experimentally). They have a high free spectral range (typically 775 nm with gratings working in the first order). Small spacing such as 25 GHz is commercially available and 5 GHz feasibility has been demonstrated. Athermal glass components down to 25 GHz spacing are manufactured with uncontrolled drifts as low as 0.35 pm/°C using commonly available glasses. These solutions are based on the traditional and mature optics technology used to manufacture millions of diffractionlimited reliable optics at low cost. The unique three-dimensional nature of these components can be exploited for advanced features requested by network designers such as add/drops, crossconnects, and routing devices. Cyclic passive routers accurately matched to the ITU frequencies in DWDM or to ITU wavelengths in CWDM have been proposed for advanced networks. Diffraction grating components can be used for high quality bidirectional links. For mono-directional or bi-directional links they have virtually unlimited numbers of channels and provide the lowest crosstalk for the higher number of channels. For low cost mass production the problems of fibre handling, that are the same with any solution, remain to be solved.

Laude, Jean-Pierre

342

Anisotropic and Heterogeneous Development of Microstructures. Combining Laboratory/Synchrotron X-rays and EBSD on a few SPD Metallic Systems  

NASA Astrophysics Data System (ADS)

The onset of Severe Plastic Deformation (SPD) regime is quite instructive on the possible origins of the nano-microstructures developed in metals and alloys. It is known that grain fragmentation and dislocation accumulation, among other defects, proceed at different paces depending fundamentally on grain orientations and active deformation mechanisms. There have been many attempts to characterize nano-microstructure anisotropy, leading all of them to sometimes contradictory conclusions. Moreover, the characterizations rely on different measurements techniques and pos-processing approaches, which can be observing different manifestations of the same phenomena. On the current presentation we show a few experimental and computer pos-processing and simulation approaches, applied to some SPD/alloy systems. Williamson-Hall and Convolutional Multiple Whole Profile (CMWP) techniques will be applied to peak broadening analysis on experimental results stemming from laboratory Cu Ka X-rays, and synchrotron radiation from LNLS (Laboratório Nacional de Luz Síncrotron, Campinas, Brazil) and Petra III line (HEMS station, at DESY, Hamburg, Germany). Taking advantage of the EBSD capability of giving information on orientational and topological characteristics of grain boundaries, microstructures, grain sizes, etc., we also performed investigations on dislocation density and Geometrically Necessary Dislocation Boundaries (GNDB) and their correlation with texture components. Orientation dependent nano-microstructures and domain sizes are shown on the scheme of generalized pole figures and discussions provide some hints on nano-microstructure anisotropy.

Bolmaro, Raúl E.; De Vincentis, Natalia S.; Benatti, Emanuel; Kliauga, Andrea M.; Avalos, Martina C.; Schell, Norbert; Brokmeier, Heinz-Günter

2014-08-01

343

Radar Backscatter Saturation with Forest Biomass: Facts and Myths  

NASA Astrophysics Data System (ADS)

In recent years, climate change policies and scientific research created a widespread interest in quantify the carbon stock and changes of global forests extending from forest patches to national and regional scales. However, because of the large spatial extent of forests, their heterogeneity from structural and species diversity causing meters to kilometer scales variations, their complex dynamics causing landscape scale differences in changes of biomass, and their continues degradation from human activities, the quantification of forest biomass from conventional inventory data alone has become a major challenge. Remote sensing techniques with Lidar and Radar are considered to be the most efficient way of estimating forest biomass at large scales and with uncertainty comparable to estimation from inventory plots. Radar backscatter and interferometric based estimation of forest biomass has been studied extensively and considered as dedicated spaceborne options of monitoring and quantifying forest biomass. However, the literature on the radar-based estimation techniques of biomass has been misleading in defining the sensitivity and lack of sensitivity, so called saturation effect of radar measurements. In this paper, I provide results from a combination of observations and model simulations to demonstrate the physical nature of the loss of sensitivity of radar backscatter to biomass, examine the biophysical that impact the sensitivity, extend the results to other radar measurements including polarimetric and interferometric modes.

Saatchi, S. S.

2012-12-01

344

Investigation of microwave backscatter from the air-sea interface  

NASA Technical Reports Server (NTRS)

Monitoring the ocean surface winds and mean ocean surface level is essential for improving our knowledge of the climate. Two instruments that may provide us with this information are satellite-based scatterometers and altimeters. However, these instruments measure the backscatter characteristics of the ocean surface from which other physical parameters, such as the wind speed or ocean surface height, are derived. To improve the algorithms or models that relate the electromagnetic backscatter to the desired physical parameters, the University of Massachusetts (UMass) Microwave Remote Sensing Laboratory (MIRSL) designed and fabricated three airborne scatterometers: a C-band scatterometer (CSCAT), Ku-band scatterometer (KUSCAT) and C/Ku-band scatterometer (EMBR). One or more of these instruments participated in the Electromagnetic Bias experiment (EM Bias), Shelf Edge Exchange Processes experiment (SEEP), Surface Wave Dynamics Experiment (SWADE), Southern Ocean Wave Experiment (SOWEX), Hurricane Tina research flights, Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), and Ladir In-space Technology Experiment (LITE). This document describes the three scatterometers, summarizes our measurement campaigns and major contributions to the scientific and engineering communities, lists the publications that resulted, and presents the degrees earned under the support of this NASA grant.

Mcintosh, Robert E.; Carswell, James R.

1995-01-01

345

Backscatter Mossbauer Spectrometer (BaMS) for extraterrestrial applications  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

346

Coherent Effects in Microwave Backscattering Models for Forrest Canopies  

NASA Technical Reports Server (NTRS)

In modeling forest canopies, several scattering mechanisms are taken into account: (1) volume scattering; (2) surface-volume interaction; and (3) surface scattering from forest floor. Depending on the structural and dielectric characteristics of forest canopies, the relative contribution of each mechanism in the total backscatter signal of an imaging radar can vary. In this paper, two commonly used first-order discrete scattering models, distorted born approximation (DBA) and radiative transfer (RT) are used to simulate the backscattered power received by polarimetric radars at P-, L-, and C-bands over coniferous and deciduous forests. The difference between the two models resides on the coherent effect in the surface-volume interaction terms. To demonstrate this point, the models are first compared based on their underlying theoretical assumptions and then according to simulation results over coniferous and deciduous forests. It is shown that by using the same scattering functions for various components of trees (i.e., leaf, branch, stem), the radiative transfer and distorted Born models are equivalent, except in low frequencies, where surface-volume interaction terms may become important, and the coherent contribution may be significant. In this case, the difference between the two models can reach up to 3 dB in both co-polarized and cross-polarized channels, which can influence the performance of retrieval algorithms.

Saatchi, Sasan S.; McDonald, Kyle C.

1997-01-01

347

Feasibility of using Backscattered Mueller Matrix Images for Bioaerosol Detection  

NASA Astrophysics Data System (ADS)

It has been shown that by looking at the backscattered radiance from an object illuminated by a laser beam one could effectively distinguish different morphologies from one another. However, if one wants to obtain all the information possible from elastic scattering either from a single particle or an ensemble of particles then one must use the Mueller matrix which contains all the polarization and radiance information available. In this talk, we will show that if we take advantage of the polarization information of the object, many more images related to the overall morphology as well as the internal structure of the object can be obtained. We will present images of the complete Mueller matrix to show the sensitivity of its sixteen components to both external and internal particle properties. We will also show that by using only one or two elements of this matrix one might be able to distinguish bioaerosols such as anthrax from more benign aerosols. We also show that the backscattering Mueller images contain more information than the forward scattering ones.

Li, Changhui; Kattawar, George W.

2006-03-01

348

Assembly for Rutherford backscattering at exactly 180{degree}  

SciTech Connect

We describe a facility which allows us to measure projectiles scattered at an angle arbitrarily near 180{degree}. The backscattered projectiles are deflected in the horizontal plane out of the incoming beam by a combination of electric and magnetic fields. The charged particles, which are spatially dispersed according to their energy, are detected by a cooled 300 mm{sup 2} ion implanted silicon detector. By a judicious choice of the relative strength of both fields we ensure that the essential parts of the spectrum will not be distorted due to an energy dependent percentage of projectiles missing the detector. As the projectiles are also dispersed according to their charge state we are able to distinguish between, e.g., singly and doubly charged He projectiles as they hit the detector at different positions. The detector can be moved in the vertical direction to continuously vary the backscattering angle between 180{degree} and 178.5{degree}. This experimental result shows for the first time the angular range to which the 180{degree} enhancement is confined. Such a device is ideally suited for investigating single crystals by uniaxial channeling blocking. {copyright} {ital 1996 American Institute of Physics.}

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

1996-05-01

349

Pascal's triangle and the simulation of backscattering spectra  

NASA Astrophysics Data System (ADS)

Applying a well-known yield equation to a stack of very thin sublayers allows accurate simulations of homogeneous, thick-target, backscattering spectra. Explicit expressions, accurate to at least third degree in the areal density for the ion energy immediately before scattering and for the detected ion energy, are found. These expressions are in terms of binomial expansions of a quantity equaling the product of the areal density multiplied by a function of stopping cross section derivatives and areal density. One iterative parameter, taken as the near-surface yield, is required to properly normalize the simulation with respect to the experimental spectrum. Several thick target spectra, produced by bombarding helium ions with energies ranging over several MeV, are simulated using both Ziegler's 1977 [J.F. Ziegler, Helium Stopping Powers and Ranges in All Elements (Pergamon, New York, 1977)] and 1985 [J.F. Ziegler, J.P. Biersack and U. Littmark, The Stopping and Range of Ions in Solids (Pergamon, New York, 1985)] stopping compilations to ascertain the impact of these differing stopping cross sections on predictions of backscattering spectra.

Bozoian, Michael

1994-04-01

350

Detection of Explosive Devices using X-ray Backscatter Radiation  

NASA Astrophysics Data System (ADS)

It is our goal to develop a coded aperture based X-ray backscatter imaging detector that will provide sufficient speed, contrast and spatial resolution to detect Antipersonnel Landmines and Improvised Explosive Devices (IED). While our final objective is to field a hand-held detector, we have currently constrained ourselves to a design that can be fielded on a small robotic platform. Coded aperture imaging has been used by the observational gamma astronomy community for a number of years. However, it has been the recent advances in the field of medical nuclear imaging which has allowed for the application of the technique to a backscatter scenario. In addition, driven by requirements in medical applications, advances in X-ray detection are continually being made, and detectors are now being produced that are faster, cheaper and lighter than those only a decade ago. With these advances, a coded aperture hand-held imaging system has only recently become a possibility. This paper will begin with an introduction to the technique, identify recent advances which have made this approach possible, present a simulated example case, and conclude with a discussion on future work.

Faust, Anthony A.

2002-09-01

351

Seabottom Backscatter Studies in the Western Continental Shelf of India  

NASA Astrophysics Data System (ADS)

In this paper, a study is initiated to observe the interaction effect of the sound signal with three different sediment bottoms in the shelf area between Cochin and Mangalore in the western continental shelf of India. An echo signal acquisition system has been designed and interfaced with the 12 kHz echosounder installed onboard ORV Sagar Kanya. The reflection coefficients including attenuation at the seawater/bottom interface are computed in the three different sediment areas based on the sediment mean grain size. The experimental coherent reflection coefficients are calculated using the attenuation corrected reflection coefficients and the normalized cross-correlation between successive backscatter echo signal waveforms in those areas. Further, analyses conducted by determining the echo peak Probability Density Function (PDF) and matching them with the experimental echo peak histograms provide root mean square (rms) roughness amplitude in the three different survey areas. The rms roughness values are used to compute the coherent reflection coefficients. An attempt to establish concurrence between the coherent reflection coefficients based upon the rms roughness amplitude and the experimental coherent reflection coefficients using the backscatter echo signals, reveals the importance of seawater/bottom interface roughness in the coarse grained sediment bottoms like sand and silty sand. The existence of microtopographic features are responsible for the seawater/bottom interface roughness. However, in the fine grained sediment area, the bottom does not contain any such feature.

Chakraborty, B.; Pathak, D.

1999-01-01

352

Particle characterisation in highly concentrated dispersions using ultrasonic backscattering method.  

PubMed

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

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

2013-03-01

353

Rutherford backscattering analysis of the failure of chlorine anodes  

SciTech Connect

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

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

1996-06-01

354

Rutherford backscattering analysis of the failure of chlorine anodes  

SciTech Connect

Rutherford Backscattering Spectrometry, carried out at the ORNL Surface Modification And Characterization Collaborative Research Center (SMAC) facility, has been applied to the nondestructive analysis of RuO[sub 2]-TiO[sub 2] electrodes of 5000 Angstroms, which mimic the DSA anodes in composition and the method of preparation. Occidental Chemical Corporation provided electrodes, which had been subjected to life time testing in H[sub 2]S04 solution, for analysis by ORNL. The results were used to test the hypothesis of degradation of theses, and similar electrodes, from a process involving a decrease in the RuO[sub 2]:TiO[sub 2] ratio at and near the electrode surface and the related decrease in the electrode electrical conductivity. The drop in electrode activity is closely linked to a decrease in Ru content, and the measured profiles show that the loss takes place across the thin RuO[sub 2]-TiO[sub 2] coating. No build up of a pure TiO[sub 2] layer is apparent. The data agree quantitatively with the critical concentration previously reported by ORNL for materials produced by ion implantation and characterized by Rutherford Backscattering Spectrometry and Photoacoustic Spectrometry. The study has brought a better understanding of the degradation process in electrodes of great technological importance, and has given a more solid background in designing new fabrication procedures for improved electrodes.

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

1996-06-01

355

Diffraction-based optical correlator  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

356

Depth from diffracted rotation.  

PubMed

The accuracy of depth estimation based on defocus effects has been essentially limited by the depth of field of the imaging system. We show that depth estimation can be improved significantly relative to classical methods by exploiting three-dimensional diffraction effects. We formulate the problem by using information theory analysis and present, to the best of our knowledge, a new paradigm for depth estimation based on spatially rotating point-spread functions (PSFs). Such PSFs are fundamentally more sensitive to defocus thanks to their first-order axial variation. Our system acquires a frame by using a rotating PSF and jointly processes it with an image acquired by using a standard PSF to recover depth information. Analytical, numerical, and experimental evidence suggest that the approach is suitable for applications such as microscopy and machine vision. PMID:16441023

Greengard, Adam; Schechner, Yoav Y; Piestun, Rafael

2006-01-15

357

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

Sommargren, G.E.

1996-08-29

358

Multilayer diffraction grating  

DOEpatents

This invention is for a reflection diffraction grating that functions at X-ray to VUV wavelengths and at normal angles of incidence. The novel grating is comprised of a laminar grating of period D with flat-topped grating bars. A multiplicity of layered synthetic microstructures, of period d and comprised of alternating flat layers of two different materials, are disposed on the tops of the grating bars of the laminar grating. In another embodiment of the grating, a second multiplicity of layered synthetic microstructures are also disposed on the flat faces, of the base of the grating, between the bars. D is in the approximate range from 3,000 to 50,000 Angstroms, but d is in the approximate range from 10 to 400 Angstroms. The laminar grating and the layered microstructures cooperatively interact to provide many novel and beneficial instrumentational advantages.

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

1990-01-01

359

Phase shifting diffraction interferometer  

DOEpatents

An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

360

Dichroic coherent diffractive imaging  

PubMed Central

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

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

2011-01-01

361

Quantum theory of light diffraction  

E-print Network

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

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

2010-11-16

362

Ultrafast X-ray diffraction  

Microsoft Academic Search

This study presents recent developments and applications of ultrafast X-ray diffraction. These include optical pump\\/X-ray probe experiments for performing ultrafast X-ray spectroscopy, time-resolved X-ray diffraction for the investigation of electronically induced solid-liquid phase transformations in semiconductors, and time-resolved X-ray diffraction for monitoring the rapid changes of the atomic configuration associated with the lattice waves.

D. von der Linde; K. Sokolowski-Tinten

2003-01-01

363

New Diffraction Results from CDF  

E-print Network

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

Christina Mesropian

2005-10-14

364

Diffraction and Vector Meson Production at HERA  

E-print Network

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

365

Kinematics of Compton backscattering x-ray source for angiography  

SciTech Connect

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

Blumberg, L.N.

1992-05-01

366

Diffraction from the Deep Sea  

NASA Astrophysics Data System (ADS)

Experimental results on soft and hard diffractive processes obtained by the CDF Collaboration in bar pp interactions are examined with emphasis on regularities that point to QCD aspects of hadronic diffraction. Data are interpreted in a phenomenological approach in which diffractive cross sections are related to the underlying inclusive parton distribution functions of the nucleon. In this approach, diffraction appears to be mediated by the exchange of low-x partons from the quark/gluon sea of the interacting nucleons subject to color constraints.

Goulianos, K.

2005-02-01

367

Electrically-programmable diffraction grating  

DOEpatents

An electrically-programmable diffraction grating. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers).

Ricco, Antonio J. (Albuquerque, NM); Butler, Michael A. (Albuquerque, NM); Sinclair, Michael B. (Albuquerque, NM); Senturia, Stephen D. (Brookline, MA)

1998-01-01

368

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

E-print Network

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

Jaffe, Jules

369

Acoustic backscatter of the 1995 flood deposit on the Eel shelf  

Microsoft Academic Search

Acoustic swath mapping and sediment box coring conducted on the continental shelf near the mouth of the Eel River revealed regional variations in acoustic backscatter that can be related to the shelf sedimentology. The acoustic-backscatter variations observed on the shelf were unusually narrow compared to the response of similar sediment types documented in other areas. However, the acoustic data revealed

Jeffry C Borgeld; John E Hughes Clarke; John A Goff; Larry A Mayer; Jennifer A Curtis

1999-01-01

370

Low-coherence enhanced backscattering: review of principles and applications for colon cancer screening  

E-print Network

Low-coherence enhanced backscattering: review of principles and applications for colon cancer the risk of colon carcinogenesis and colonoscopy-free screening for colorectal cancer CRC . © 2006 Society; enhanced backscattering; low coherence; elas- tic light scattering; spectroscopy; colorectal cancer. Paper

Ottino, Julio M.

371

Simulation-guided optimization of small-angle analyzer geometry in the neutron backscattering spectrometer SPHERES  

SciTech Connect

The resolution of neutron backscattering spectrometers deteriorates at small scattering angles where analyzers deviate from exact backscattering. By reducing the azimuth angle range of the analyzers, the resolution can be improved with little loss of peak intensity. Measurements at the spectrometer SPHERES are in excellent agreement with simulations, which proves the dominance of geometric effects.

Wuttke, Joachim; Zamponi, Michaela [Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, Lichtenbergstraße 1, 85747 Garching (Germany)] [Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at MLZ, Lichtenbergstraße 1, 85747 Garching (Germany)

2013-11-15

372

An investigation of backscatter power spectra from cells, cell pellets and microspheres  

Microsoft Academic Search

It has been previously shown that high frequency ultrasound (20-100 MHz) can be used to detect cellular structure changes in tissues and cell ensembles. However, the changes seen in the backscattered ultrasound intensity and frequency spectrum are not fully understood. In this paper we attempt to better understand the nature of these changes by examination of the backscatter power spectra

Michael C Kolios; L. Taggart; R. E. Baddour; F. S. Foster; J. W. Hunt; G. J. Czarnota; M. D. Sherar

2003-01-01

373

The measurement of ultrasound backscattering from cell pellet biophantoms and tumors ex vivo  

E-print Network

The measurement of ultrasound backscattering from cell pellet biophantoms and tumors ex vivo Aiguo from the tumors is 100% volume fraction cell pellets of the same cell lines. Cell pellets and ex vivo and backscatter coefficient (BSC) are estimated. BSC compari- sons are made between cell pellets and tumors

Illinois at Urbana-Champaign, University of

374

Relationships between extinction, absorption, backscattering, and mass content of sulfuric acid aerosols  

Microsoft Academic Search

Linear relationships between aerosol extinction, absorption, backscatter, and mass content are derived for polydispersions of sulfuric acid aerosols. These relationships are independent of the form of the size distribution and are a consequence of approximating the corresponding Mie efficiency factors (the extinction efficiency Q\\/sub e\\/, the absorption efficiency Q\\/sub a\\/, and the backscatter gain G) by linear functions of the

R. G. Pinnick; S. G. Jennings; P. Chylek

1980-01-01

375

Stratospheric Backscatter, Extinction, and Lidar Ratio Profiling After the Mt. Pinatubo Eruptions  

NASA Technical Reports Server (NTRS)

Since August 1991 the stratospheric aerosol layer is continuously monitored with a combination Raman elastic-backscatter lidar, groundbased systems. XeCl excimer laser is used as the radiation source. Signals elastically backscattered from air molecules and particles and inelastically Raman backscattered from nitrogen molecules are detected. The measurements of these two signal profiles up to 35 km height allows the separate and independent determination of aerosol extinction and backscatter properties in the perturbed lower stratosphere. The extinction coefficient is derived from the nitrogen Raman signal profile, while the backscatter coefficient is obtained from the elastic-to-inelastic backscatter signal ratio. In this way, also the extinction-to-backscatter, or lidar, ratio profile is determined. For the first time, lidar ratios are determined in the perturbed stratospheric layer by the use of remote sensing only. The lidar ratio contains information about the size range of the stratospheric particles which are assumed to be sulfuric acid droplets, and it is needed in the calculation of aerosol optical properties from data taken with a typical backscatter lidar.

Ansmann, Albert; Schulze, Christoph; Wandinger, Ulla; Weitkamp, Claus; Michaelis, Walfried

1992-01-01

376

Mueller matrix approach for determination of optical rotation in chiral turbid media in backscattering geometry  

Microsoft Academic Search

For in vivo determination of optically active (chiral) substances in turbid media, like for example glucose in human tissue, the backscattering geometry is particularly convenient. However, recent polarimetric measurements performed in the backscattering geometry have shown that, in this geometry, the relatively small rotation of the polarization vector arising due to the optical activity of the medium is totally swamped

S. Manhas; M. K. Swami; P. Buddhiwant; N. Ghosh; P. K. Gupta; J. Singh

2006-01-01

377

Correlation of sidescan backscatter with grain size distribution of surficial seabed sediments  

Microsoft Academic Search

The dependence of acoustic backscatter on sediment grain size distribution is examined using dual frequency (100 and 410 kHz) sidescan sonar and 22 sediment grab samples from the Loch Linnhe artificial reef site on the west coast of Scotland. The sidescan data were processed to remove an empirically estimated average grazing angle dependence on backscatter. The processed data were analysed

J. S. Collier; C. J. Brown

2005-01-01

378

Estimating surface oil extent from the Deepwater Horizon oil spill using ASCAT backscatter  

Microsoft Academic Search

This paper examines a method of estimating surface oil extent by comparing ASCAT-measured backscatter with the expected backscatter using the GMF and numerical weather predicted (NWP) winds. Background information on ASCAT, the GMF, and the effects of surface oil are first presented. Our methodology for surface oil extent mapping follows. Results are shown for selected case studies and the performance

Richard D. Lindsley; David G. Long

2011-01-01

379

Analysis of discrete oblique ionogram traces in sweep-frequency sky-wave high resolution backscatter  

Microsoft Academic Search

A method is presented for the analysis of discrete oblique ionogram traces observed in high resolution sweep-frequency sky-wave backscatter technique to obtain quasiparabolic ionospheric layer parameters. The method employs three data points on the oblique ionogram with one of the data points being the point of coincidence of the oblique ionogram trace with the leading edge of the backscatter. The

N. Narayana Rao

1975-01-01

380

A method of determining horizontal structure of the ionosphere from backscatter ionograms  

Microsoft Academic Search

We have developed a technique for oblique backscatter sounding (OBS) ionogram inversion as a diagnostic tool for the horizontally inhomogeneous structure of the ionosphere. Input data for the method include the leading edge of a backscatter ionogram that is measured through soundings in a given direction, and the vertical electron density profile measured over the sounding station or over some

Olga V. Fridman; Sergey V. Fridman

1994-01-01

381

Coherent light backscattering by refractive turbulence in lidar sounding of the atmosphere and the ocean  

Microsoft Academic Search

Theoretical analysis of light waves backscattering by a layer of random medium with weak refractive index fluctuations is presented, and some estimates for the effect contribution to lidar signals in atmospheric and ocean remote sounding are given. It is shown that coherent light backscattering by a thin turbulent layer may be strong enough compared with incoherent component caused by dispersed

Yurij I. Kopilevich

1995-01-01

382

The Channel Backscattering Characteristics of Sub100nm CMOS Devices with Different Channel\\/Substrate Orientations  

Microsoft Academic Search

The channel backscattering and injection velocity of carriers in advanced CMOS devices are the two key parameters for achieving high drain current enhancement. For the first time, an extensive study of these transport parameters for different substrate orientations has been evaluated for both nMOSFET and pMOSFET. By suitably choosing the substrate orientation, it may achieve a reduced backscattering and an

Y. J. Tsai; S. S. Chung; P. W. Liu; C. H. Tsai; Y. H. Lin; C. T. Tsai; G. H. Ma; S. C. Chien; S. W. Sun

2007-01-01

383

THEORETICAL ESTIMATION AND EXPERIMENTAL TECHNIQUES FOR THE DETERMINATION OF THE TEMPERATURE DEPENDENCE OF BACKSCATTERED ULTRASONIC POWER  

E-print Network

DEPENDENCE OF BACKSCATTERED ULTRASONIC POWER William L. Straube and R. Martin Arthur* Mallinckrodt Institute-section of a small scatterer. Backscattered power increased nearly logarithmically with temperature over the rangeB for the aqueous-based scatterer over that temperature range. The primary deterrent to in vitro experimental

Arthur, R. Martin

384

Frequency and concentration dependence of the ultrasonic backscatter coefficient in a soft tissue  

E-print Network

Frequency and concentration dependence of the ultrasonic backscatter coefficient in a soft tissue ranged from 50 to 200 g of graphite per liter of gelatin. The backscatter coefficient was evaluated using both Sigelman and Reid method and Chen method in a frequency range around 5 MHz. The evolution

Boyer, Edmond

385

Motion Compensation for Temperature Imaging using the Change in Ultrasonic Backscattered Energy  

E-print Network

Motion Compensation for Temperature Imaging using the Change in Ultrasonic Backscattered Energy and in-vitro experiments [2] verified that the change in backscattered ultrasonic energy (CBE) is monotonic (approximately 0.2~0.3dB/oC) with temperature in the hyperthermia range, motivating the usage

Arthur, R. Martin

386

Separation of differential propagation phase and differential backscatter phase in polarisation diversity radar  

Microsoft Academic Search

The total phase measured from a polarization-diversity radar is the sum of differential propagation phase and backscatter phase. An algorithm is presented to obtain differential propagation phase from the total phase by separating the backscatter phase. This algorithm is independent of raindrop size distribution and frequency.

A. R. Holt; J. Tan

1992-01-01

387

24th International Laser Radar Conference BACKSCATTER NEPHELOM.ETER TO CALIBRATE SCANNING LIDAR  

E-print Network

;(h) is the power of the backscatter signal measured at the height h for elevation angle 24th International Laser Radar Conference BACKSCATTER NEPHELOM.ETER TO CALIBRATE SCANNING LIDAR-grade instrument, which operates at the wavelength 355 nm, will be co-located with a scanning-lidar at measurement

388

Study of backscattering in alpha-particle sources with the new code AlfaMC  

NASA Astrophysics Data System (ADS)

The activity of alpha-particle sources with negligible thickness can be absolutely determined using 2? counting geometry detectors, requiring corrections for backscattering from the source backing. The experimental determination of these corrections is subject to large uncertainties, because the contribution of the backscattered alpha particles to the total counting is generally very low. An interesting alternative is then to use Monte Carlo methods which simulate the transport of alpha-particles into the source. The programme AlfaMC, a new Monte Carlo code developed to simulate specifically the transport of alpha particles, was here applied to the study of the backscattering in alpha-particle sources. Energy and angular distributions for the backscattered alpha particles were deeply analysed based on a multiple scattering process, as a result of a large number of weak collisions with atomic electrons. Some calculated values for the backscattering coefficient were compared with experimental values, showing a good agreement.

Vargas, M. Jurado; Timón, A. Fernández

2015-01-01

389

[Obtaining aerosol backscattering coefficient using pure rotational Raman-Mie scattering spectrum].  

PubMed

Both the traditional Klett and Fernald methods used to obtain atmospheric aerosol backscattering coefficient require the hypothesis of relationship between the extinction coefficient and backscattering coefficient, and this will bring error. According to the theory that the pure rotational Raman backscattering coefficient is only related to atmospheric temperature and pressure, a new method is presented for inverting aerosol backscattering coefficient, which needed the intensity of elastic scattering and rotational Raman combined with atmospheric temperature and pressure obtained with the sounding balloons in this article. This method can not only eliminate the errors of the traditional Klett and Fernald methods caused by the hypothesis, but also avoid the error caused by the correction of the overlap. Finally, the aerosol backscattering coefficient was acquired by using this method and the data obtained via the Raman-Mie scattering Lidar of our lab. And the result was compared with that of Klett and Fernald. PMID:23387171

Rong, Wei; Chen, Si-Ying; Zhang, Yin-Chao; Chen, He; Guo, Pan

2012-11-01

390

A C-band backscatter model for lake ice in Alaska  

NASA Technical Reports Server (NTRS)

ERS-1 SAR imagery of lake ice growing on shallow tundra lakes in northern Alaska shows interesting radar backscatter variations. Based on the analysis of ice cores from these lakes, a multi-layer backscatter model comprised of the following elements has been developed: (1) specular air-ice; ice-water and ice-frozen soil boundaries; (2) an ice layer of variable thickness; (3) ice sub-layers with air inclusions of variable density, size and shape including spheres, prolate spheroids, and cylinders of finite length. Preliminary model results confirm that backscatter is a sensitive function of greater reflectivity than from an ice-frozen soil interface. The model has also been tested using bubble data derived from ice cores in April 1992. The modelled backscatter is compared with backscatter derived from ERS-1 SAR images obtained at the same time as the fieldwork.

Wakabayashi, H.; Weeks, W. F.; Jeffries, M. O.

1993-01-01

391

Polarized Rayleigh back-scattering from individual semiconductor nanowires.  

PubMed

A complete understanding of the interaction between electromagnetic radiation and semiconductor nanowires (NWs) is required in order to further develop a new generation of opto-electronic and photonic devices based on these nanosystems. The reduced dimensionality and high aspect ratio of nanofilaments can induce strong polarization dependence of the light absorption, emission and scattering, leading in some cases to the observation of optical antenna effects. In this work we present the first systematic study of polarized Rayleigh back-scattering from individual crystalline semiconductor NWs with known crystalline structure, orientation and diameters. To explain our experimental Rayleigh polar patterns, we propose a simple theory that relies on a secondary calculation of the volume-averaged internal electromagnetic fields inside the NW. These results revealed that the internal and emitted field can be enhanced depending on the polarization with respect to the NW axis; we also show that this effect strongly depends on the NW diameter. PMID:20634572

Zhang, Duming; Wu, Jian; Lu, Qiujie; Gutierrez, Humberto R; Eklund, Peter C

2010-08-01

392

Ocean Raman Scattering in Satellite Backscatter UV Measurements  

NASA Technical Reports Server (NTRS)

Ocean Raman scattering significantly contributes to the filling-in of solar Fraunhofer lines measured by satellite backscatter ultraviolet (buy) instruments in the cloudless atmosphere over clear ocean waters. A model accounting for this effect in buy measurements is developed and compared with observations from the Global Ozone Monitoring Experiment (GONE). The model extends existing models for ocean Raman scattering to the UV spectral range. Ocean Raman scattering radiance is propagated through the atmosphere using a concept of the Lambert equivalent reflectively and an accurate radiative transfer model for Rayleigh scattering. The model and observations can be used to evaluate laboratory measurements of pure water absorption in the UV. The good agreement between model and observations suggests that buy instruments may be useful for estimating chlorophyll content.

Vasilkov, Alexander P.; Joiner, Joanna; Gleason, James; Bhartia, Pawan; Bhartia, P. K. (Technical Monitor)

2002-01-01

393

Microwave backscattering and emission model for grass canopies  

NASA Technical Reports Server (NTRS)

A two-layer model is developed that treats the grass canopy as a collection of randomly oriented elliptical dielectric discs over a layer of thatch with underlying soil surface. The distorted Born approximation in conjunction with the Peake formulation is used to calculate the backscattering coefficient and the emissivity from the canopy. Two particular features of this model which are unique for grass canopies are the variation of the canopy structure and the presence of the thatch layer. The basic parameters in the model such as the size and orientation of grass blades, dielectric constant of soil and vegetation, and thickness and water content of the thatch layer have been obtained from ground truth data. To interpret the available experimental observations of grasslands, numerical results from both passive and active models at L-band (1.4 GHz) are generated and various scattering and emission properties of the grass canopies are discussed.

Saatchi, Sasan S.; Lang, Roger H.; Levine, David M.

1991-01-01

394

Double scattering in grazing angle Rutherford backscattering spectra  

NASA Astrophysics Data System (ADS)

Developments in the analytic model for double scattering in Rutherford backscattering spectra are presented. It is shown that, in grazing angle of incidence spectra of thin films, the main contribution to the low energy tails comes from particles that after the first collision have a path nearly parallel to the surface of the sample. Thus collisions with small scattering angle must be included, since they are the only way of achieving such paths. In bulk samples, these trajectories must also be included. Particle loss as the beam enters the sample, as well as angular dependent screening, are taken into account in the model developed. The effect of lateral spread due to multiple scattering is considered, and its influence in the double scattering spectrum is calculated. It is found to be important in the measurement of ultra-thin films in grazing geometry.

Barradas, N. P.

2004-09-01

395

Unusual Radar Backscatter along the Northern Rim of Imbrium Basin  

NASA Technical Reports Server (NTRS)

A viewgraph presentation of the unusual radar backscatter properties along the Northern Rim of Imbrium Basin is shown. The contents include: 1) Visual and Infrared Observations of Moon; 2) Radar Observations of Moon; 3) Lunar Orbiter Photographs Geologic Setting; 4) 70-cm Radar Data; 5) .70-cm Radar Dark Halo Craters; 6) 3.8-cm Radar Data; 7) 7.5-m Radar Data; 8) 70cm, 3.8 cm and 7.5-m Radar Data; 9) Optical and Infrared Data; 10) Plato Rilles; 11) Isopachs of Crater Ejecta; 12) Plato-like Craters; 13) Observation Summary; 14) Interpretation Matrix; 15) Dark Halo Diameters vs. Crater Size; and 16) Radar Geologic Column.

Thompson, Thomas W.; Campbell, Bruce A.; Ghent, Rebecca R.; Hawke, B. Ray; Leverington, David W.

2006-01-01

396

Backscatter absorption gas imaging systems and light sources therefore  

DOEpatents

The location of gases that are not visible to the unaided human eye can be determined using tuned light sources that spectroscopically probe the gases and cameras that can provide images corresponding to the absorption of the gases. The present invention is a light source for a backscatter absorption gas imaging (BAGI) system, and a light source incorporating the light source, that can be used to remotely detect and produce images of "invisible" gases. The inventive light source has a light producing element, an optical amplifier, and an optical parametric oscillator to generate wavelength tunable light in the IR. By using a multi-mode light source and an amplifier that operates using 915 nm pump sources, the power consumption of the light source is reduced to a level that can be operated by batteries for long periods of time. In addition, the light source is tunable over the absorption bands of many hydrocarbons, making it useful for detecting hazardous gases.

Kulp, Thomas Jan (Livermore, CA); Kliner, Dahv A. V. (San Ramon, CA); Sommers, Ricky (Oakley, CA); Goers, Uta-Barbara (Campbell, NY); Armstrong, Karla M. (Livermore, CA)

2006-12-19

397

Low Arabian dust extinction-to-backscatter ratio  

NASA Astrophysics Data System (ADS)

Compared to typical values of 50-60 sr of the extinction-to-backscatter ratio (lidar ratio) at 532 nm of western Saharan mineral dust, low dust lidar ratios from 33.7±6.7 to 39.1±5.1 sr were derived from polarization lidar observations at Limassol, Cyprus (34°N, 33°E) during an outbreak of Arabian dust mainly from Syria in September 2011, indicated by particle linear depolarization ratios up to 28%-35%. The applied new polarization-lidar/photometer method for the extraction of the dust-related lidar-ratio information from the lidar data is outlined, and the results of the dust outbreak which lasted over several days are discussed. The results confirm an Aerosol Robotic Network photometer study on Arabian dust lidar ratios.

Mamouri, R. E.; Ansmann, A.; Nisantzi, A.; Kokkalis, P.; Schwarz, A.; Hadjimitsis, D.

2013-09-01

398

A dynamic forcing scheme incorporating backscatter for hybrid simulation  

NASA Astrophysics Data System (ADS)

In this paper, a dynamic forcing scheme incorporating backscatter is proposed in order to remove the artificial buffer layer in a hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy simulation (LES) approach. In contrast to previous forcing techniques, the proposed forcing is determined dynamically from the flow field itself, and does not require any extraction of turbulent fields from reference direct numerical simulation (DNS) or high-resolution LES databases. Transport equations for the resolved turbulent stresses and kinetic energy are introduced to investigate the effects of dynamic forcing on reduction of the thickness and impact of the artificial buffer layer. The proposed forcing model has been tested in the context of turbulent channel flows with Reynolds numbers Re? = 650 and 1020 (based on the wall friction velocity and half channel height). In order to validate the hybrid RANS/LES approach, flow statistics obtained from the simulations have been thoroughly compared against the available DNS data.

Xun, Qian-Qiu; Wang, Bing-Chen

2014-07-01

399

STS-34 Galileo / Shuttle Solar Backscatter UV (SSBUV) flight configurations  

NASA Technical Reports Server (NTRS)

Artist concept of Atlantis', Orbiter Vehicle (OV) 104's, payload bay (PLB) titled STS-34 GALILEO/SSBUV shows the flight configuration of the Shuttle Solar Backscatter Ultraviolet (UV) (SSBUV) and the Galileo spacecraft and inertial upper stage (IUS). An inset shows the details of the SSBUV get away special (GAS) canisters. SSBUV canisters will be mounted on a GAS adapter beam assembly (GABA) or gas bridge assembly (GBA) on OV-104's PLB starboard wall. One GAS canister has a motorized door assembly (MDA). During STS-34, SSBUV instrument will calibrate similar ozone measuring space-based instruments on the National Oceanic and Atmospheric Administration's (NOAA's) TIROS satellites (NOAA-9 and NOAA-11). SSBUV uses the Space Shuttle's orbital flight path to assess instrument performance by directly comparing data from identical instruments aboard TIROS spacecraft, as the Shuttle and the satellite pass over the same Earth location within a one hour window. SSBUV is managed by Goddard Space

1989-01-01

400

Directional spectra of ocean waves from microwave backscatter  

NASA Technical Reports Server (NTRS)

The paper presents an analysis of two proposed microwave radar techniques for measuring ocean wave directional spectra. Tomiyasu's (1971) short pulse idea and Barrick's (1972) two-frequency correlation idea are regarded - independent of transmitted waveform - as essentially two alternative detection systems for modulated noise. Together, the two systems constitute a general detection system for modulated noise described some years ago by Parzen and Shiren (1956). A frequency domain analysis for backscatter on arbitrary incident waveform is given, and an interesting physical optics solution for the generalized fourth-order moments of the scattering matrix is obtained. It is shown that the present narrowband version of Barrick's two-frequency idea is impractical, and that the proper application of Barrick's idea is to wide band signals.

Jackson, F. C.

1974-01-01

401

Broadband ultrasonic backscattering applied to nondestructive characterization of materials.  

PubMed

A simple method based on the spectrum features of the backscattered signal is proposed to the assessment of scatterers size. The method takes advantage of the band-limited response of the scattering media to an incident broadband pulse. The single to multiple scattering regime transition determines this limited frequency content, which is strongly related to scatterer size. The method is applied to the estimation of graphite particle sizes in cast irons. Good quantitative correlation is obtained between graphite sizes measured by metallography and that obtained using this new ultrasonic method, in spite of the band limitations of the ultrasonic system used in the experiment. By this method, the absolute mean value of the scatterer size can be evaluated, provided that a reasonably good estimate of the concentration of particles is known. PMID:15301002

Kruger, Silvio E; Rebello, João M A; Charlier, Jacques

2004-07-01

402

Snow backscatter in the 1-8 GHz region  

NASA Technical Reports Server (NTRS)

The 1-8 GHz microwave active spectrometer system was used to measure the backscatter response of snow covered ground. The scattering coefficient was measured for all linear polarization combinations at angles of incidence between nadir and 70 deg. Ground truth data consisted of soil moisture, soil temperature profile, snow depth, snow temperature profile, and snow water equivalent. The radar sensitivity to snow water equivalent increased in magnitude with increasing frequency and was almost angle independent for angles of incidence higher than 30 deg, particularly at the higher frequencies. In the 50 deg to 70 deg angular range and in the 6 to 8 GHz frequency range, the sensitivity was typically between -0.4 dB/.1 g/sq cm and -0.5 dB/,1 g/sq cm, and the associated linear correlation coefficient had a magnitude of about 0.8.

Ulaby, F. T.

1976-01-01

403

Back-scatter based whispering gallery mode sensing  

PubMed Central

Whispering gallery mode biosensors allow selective unlabelled detection of single proteins and, combined with quantum limited sensitivity, the possibility for noninvasive real-time observation of motor molecule motion. However, to date technical noise sources, most particularly low frequency laser noise, have constrained such applications. Here we introduce a new technique for whispering gallery mode sensing based on direct detection of back-scattered light. This experimentally straightforward technique is immune to frequency noise in principle, and further, acts to suppress thermorefractive noise. We demonstrate 27?dB of frequency noise suppression, eliminating frequency noise as a source of sensitivity degradation and allowing an absolute frequency shift sensitivity of 76?kHz. Our results open a new pathway towards single molecule biophysics experiments and ultrasensitive biosensors. PMID:24131939

Knittel, Joachim; Swaim, Jon D.; McAuslan, David L.; Brawley, George A.; Bowen, Warwick P.

2013-01-01

404

Backscattering and Nonparaxiality Arrest Collapse of Damped Nonlinear Waves  

NASA Technical Reports Server (NTRS)

The critical nonlinear Schrodinger equation (NLS) models the propagation of intense laser light in Kerr media. This equation is derived from the more comprehensive nonlinear Helmholtz equation (NLH) by employing the paraxial approximation and neglecting the backscattered waves. It is known that if the input power of the laser beam (i.e., L(sub 2) norm of the initial solution) is sufficiently high, then the NLS model predicts that the beam will self-focus to a point (i.e.. collapse) at a finite propagation distance. Mathematically, this behavior corresponds to the formation of a singularity in the solution of the NLS. A key question which has been open for many years is whether the solution to the NLH, i.e., the 'parent' equation, may nonetheless exist and remain regular everywhere, in particular for those initial conditions (input powers) that lead to blowup in the NLS. In the current study, we address this question by introducing linear damping into both models and subsequently comparing the numerical solutions of the damped NLH (boundary-value problem) with the corresponding solutions of the damped NLS (initial-value problem). Linear damping is introduced in much the same way as done when analyzing the classical constant-coefficient Helmholtz equation using the limiting absorption principle. Numerically, we have found that it provides a very efficient tool for controlling the solutions of both the NLH and NHS. In particular, we have been able to identify initial conditions for which the NLS solution does become singular. whereas the NLH solution still remains regular everywhere. We believe that our finding of a larger domain of existence for the NLH than that for the NLS is accounted for by precisely those mechanisms, that have been neglected when deriving the NLS from the NLH, i.e., nonparaxiality and backscattering.

Fibich, G.; Ilan, B.; Tsynkov, S.

2002-01-01

405

Feasibility of using backscattered muons for archeological imaging  

NASA Astrophysics Data System (ADS)

Use of nondestructive methods to accurately locate and characterize underground objects such as rooms and tools found at archeological sites is ideal to preserve these historic sites. High-energy cosmic ray muons are very sensitive to density variation and have been used to image volcanoes and archeological sites such as the Egyptian and Mayan pyramids. Muons are subatomic particles produced in the upper atmosphere that penetrate the earth's crust up to few kilometers. Their absorption rate depends on the density of the materials through which they pass. Measurements of muon flux rate at differing directions provide density variations of the materials between the muon source (cosmic rays and neutrino interactions) and the detector, much like a CAT scan. Currently, muon tomography can resolve features to the sub-meter scale making it useful for this type of work. However, the muon detector must be placed below the target of interest. For imaging volcanoes, the upper portion is imaged when the detector is placed on the earth's surface at the volcano's base. For sites of interest beneath the ground surface, the muon detector would need to be placed below the site in a tunnel or borehole. Placing the detector underground can be costly and may disturb the historical site. We will assess the feasibility of imaging the subsurface using upward traveling muons, to eliminate the current constraint of positioning the detector below the target. This work consists of three parts 1) determine the backscattered flux rate from theory, 2) distinguish backscattered from forward scattered muons at the detector, and 3) validate the theoretical results with field experimentation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Bonal, N.; Preston, L. A.

2013-12-01

406

Impact of Rayleigh Backscattering on Stimulated Brillouin Scattering threshold evaluation for 10Gb\\/s NRZ-OOK signals  

Microsoft Academic Search

We experimentally verified a decrease of stimulated Brillouin scattering threshold for 10 Gb\\/s NRZ-OOK signals with respect to theoretical predictions. We relate this reduction to Rayleigh backscattering interaction with Stokes backscattered spectrum. BER curves are shown.

M. Ferrario; Lucia Marazzi; Pierpaolo Boffi; Aldo Righetti; Mario Martinelli

2008-01-01

407

Pinwheel patterns and powder diffraction  

Microsoft Academic Search

Pinwheel patterns and their higher dimensional generalisations display continuous circular or spherical symmetries in spite of being perfectly ordered. The same symmetries show up in the corresponding diffraction images. Interestingly, they also arise from amorphous systems, and also from regular crystals when investigated by powder diffraction. We present first steps and results towards a general frame to investigate such systems,

Michael Baake; D. Frettlöh; Uwe Grimm

2007-01-01

408

Color Perception with Diffraction Gratings.  

ERIC Educational Resources Information Center

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

Kruglak, Haym; Campbell, Don

1983-01-01

409

The construction of a high resolution crystal backscattering spectrometer HERMES I  

SciTech Connect

There is a need in the United States for a state-of-the-art, cold-neutron, crystal backscattering spectrometer (CBS) designed to investigate the structure and dynamics of condensed matter systems by the simultaneous utilization of long wavelength elastic diffraction and high-energy-resolution inelastic scattering. Cold neutron spectroscopy with CBS-type instruments has already made many important contributions to the study of atomic and molecular diffusion in biomaterials, polymers, semiconductors, liquid crystals, superionic conductors and the like. Such instruments have also been invaluable for ultra high resolution investigations of the low-lying quantum tunneling processes that provide direct insight into the dynamical response of solids at the lowest energies. Until relatively recently, however, all such instruments were located at steady-state reactors. This proposal describes HERMES I (High Energy Resolution Machines I) a CBS intended for installation at the LANSCE pulsed neutron facility of Los Alamos National Laboratory. As explained in detail in the main text, the authors propose to construct an updated, high-performance CBS which incorporates neutron techniques developed during the decade since IRIS was built, i.e., improved supermirror technology, a larger area crystal analyzer and high efficiency wire gas detectors. The instrument is designed in such a way as to be readily adaptable to future upgrades. HERMES I, they believe, will substantially expand the range and flexibility of neutron investigations in the United States and open new and potentially fruitful directions for condensed matter exploration. This document describes a implementation plan with a direct cost range between $4.5 to 5.6 M and scheduled duration of 39--45 months for identified alternatives.

Larese, J.Z.

1998-11-01

410

Impact of diurnal variation in vegetation water content on radar backscatter of maize during water stress  

NASA Astrophysics Data System (ADS)

Microwave emission and backscatter of vegetated surfaces are influenced by vegetation water content (VWC), which varies in response to availability of soil moisture in the root zone. Understanding the influence of diurnal VWC dynamics on radar backscatter will improve soil moisture retrievals using microwave remote sensing, and will provide insight into the potential use for radar to directly monitor vegetation water status. The goal of this research is to investigate the effect of diurnal variation in VWC of an agricultural canopy on backscatter for different radar configurations. Water stress was induced in a corn (Zea mays) canopy near Citra, Florida, between September 1 and October 20, 2013. Diurnal destructive samples from the canopy were collected to determine leaf, stalk and total VWC. Water stress was quantified by calculating the evaporation deficit and measuring the soil water tension. The water-cloud model was used to model the influence of VWC and soil moisture variations on backscatter for a range of frequencies, polarizations and incidence angles. Furthermore, radar backscatter time series was simulated to show the effect of water stress on the diurnal variation in backscatter due to VWC. Results of this study show the very significant effects that VWC dynamics have on radar backscatter. We also highlight the potential for vegetation and soil water status monitoring using microwave remote sensing.

van Emmerik, Tim; Steele-Dunne, Susan; Judge, Jasmeet; van de Giesen, Nick

2014-05-01

411

100 keV electron backscattered range and coefficient for silicon.  

SciTech Connect

The authors have measured the range and intensity of backscattered electrons in silicon from a 100 keV source using a process independent method. Backscattered electrons contributed to the total dose of features written in a negative tone electron beam resist. Instead of measuring the height of the resist and using a contrast curve to convert the resist height to dose, the heights of the features were made equal by adjusting the backscattered contribution through dose assignments. Creating features of equal height eliminated the need to use a contrast curve to convert from resist height to total dose. Also, it allowed for measurements of the backscattered contribution from larger distances. Using a circularly symmetric torus pattern, the three-dimensional backscatter problem was reduced to a 1-dimensional Gaussian form. The authors measured the range of the backscattered electrons, {beta}, to be 31.08 {+-} 0.06 {micro}m. By varying the writing dose of the pattern, we determined the backscatter coefficient, {eta}, to be 0.63 {+-} 0.03.

Czaplewski, D.A.; Ocola, L.E. (Center for Nanoscale Materials)

2012-01-01

412

Lamb wave diffraction tomography  

NASA Astrophysics Data System (ADS)

As the worldwide aviation fleet continues to age, methods for accurately predicting the presence of structural flaws, such as hidden corrosion and disbonds, that compromise air worthiness become increasingly necessary. Ultrasonic guided waves, Lamb waves, allow large sections of aircraft structures to be rapidly inspected. However, extracting quantitative information from Lamb wave data has always involved highly trained personnel with a detailed knowledge of mechanical waveguide physics. In addition, human inspection process tends to be highly subjective, slow and prone to errors. The only practical alternative to traditional inspection routine is a software expert system capable of interpreting data with minimum error and maximum speed and reliability. Such a system would use the laws of guided wave propagation and material parameters to help signal processing algorithms automatically extract information from digitized waveforms. This work discusses several practical approaches to building such an expert system. The next step in the inspection process is data interpretation, and imaging is the most natural way to represent two-dimensional structures. Unlike conventional ultrasonic C-scan imaging that requires access to the whole inspected area, tomographic algorithms work with data collected over the perimeter of the sample. Combined with the ability of Lamb waves to travel over large distances, tomography becomes the method of choice for solving NDE problems. This work explores different tomographic reconstruction techniques to graphically represent the Lamb wave data in quantitative maps that can be easily interpreted by technicians. Because the velocity of Lamb waves depends on the thickness, the traveltimes of the fundamental modes can be converted into a thickness map of the inspected region. Lamb waves cannot penetrate through holes and other strongly scattering defects and the assumption of straight wave paths, essential for many tomographic algorithms, fails. Diffraction tomography is a way to incorporate scattering effects into tomographic algorithms in order to improve image quality and resolution. This work describes the iterative reconstruction procedure developed for the Lamb Wave tomography and allowing for ray bending correction for imaging of moderately scattering objects.

Malyarenko, Eugene Valentinovich

413

Atmospheric aerosol backscatter measurements using a tunable coherent CO2 lidar  

NASA Technical Reports Server (NTRS)

Measurements of atmospheric aerosol backscatter coefficients, using a coherent CO2 lidar at 9.25- and 10.6-micron wavelengths, are described. Vertical profiles of the volume backscatter coefficient beta have been measured to a 10-km altitude over the Pasadena, CA, region. These measurements indicate a wide range of variability in beta both in and above the local boundary layer. Certain profiles also indicate a significant enhancement in beta at the 9.25-micron wavelength compared with beta at the 10.6-micron wavelength, which possibly indicates a major contribution to the volume backscatter from ammonium sulfate aerosol particles.

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

1984-01-01

414

Modification of Spalart-Allmaras model with consideration of turbulence energy backscatter using velocity helicity  

NASA Astrophysics Data System (ADS)

The correlation between the velocity helicity and the energy backscatter is proved in a DNS case of 256 3-grid homogeneous isotropic decaying turbulence. The helicity is then proposed to be employed to improve turbulence models and SGS models. Then Spalart-Allmaras turbulence model (SA) is modified with the helicity to take account of the energy backscatter, which is significant in the region of corner separation in compressors. By comparing the numerical results with experiments, it can be concluded that the modification for SA model with helicity can appropriately represent the energy backscatter, and greatly improves the predictive accuracy for simulating the corner separation flow in compressors.

Liu, Yangwei; Lu, Lipeng; Fang, Le; Gao, Feng

2011-06-01

415

Distributed Optical Fiber Vibration Sensor Based on Rayleigh Backscattering  

NASA Astrophysics Data System (ADS)

This thesis includes studies of developing distributed optical fiber vibration sensor based on Rayleigh backscattering with broad frequency response range and high spatial resolution. Distributed vibration sensor based on all-polarization-maintaining configurations of the phase-sensitive optical time domain reflectometry (OTDR) is developed to achieve high frequency response and spatial resolution. Signal fading and noise induced by polarization change can be mitigated via polarization-maintaining components. Pencil-break event is tested as a vibration source and the layout of the sensing fiber part is designed for real applications. The spatial resolution is 1m and the maximum distance between sensing fiber and vibration event is 18cm. Wavelet denoising method is introduced to improve the performance of the distributed vibration sensor based on phase-sensitive OTDR in standard single-mode fiber. Noise can be reduced more effectively by thresholding the wavelet coefficient. Sub-meter spatial resolution is obtained with a detectable frequency up to 8 kHz. A new distributed vibration sensor based on time-division multiplexing (TDM) scheme is also studied. A special probe waveform including a narrow pules and a quasi-continuous wave can combine the conventional phase-sensitive OTDR system and polarization diversity scheme together in one single-mode fiber without crosstalk. Position and frequency of the vibration can be determined by these two detection systems consecutively in different time slots. Vibration event up to 0.6 MHz is detected with 1m spatial resolution along a 680m single-mode sensing fiber. Continuous wavelet transform (CWT) is investigated to study the non-stationary vibration events measured by our phase OTDR system. The CWT approach can access both frequency and time information of the vibration event simultaneously. Distributed vibration measurements of 500Hz and 500Hz to 1 kHz sweep events over 20 cm fiber length are demonstrated using a single-mode fiber. Optical frequency-domain reflectometry (OFDR) for vibration sensing is proposed for the first time. The local Rayleigh backscatter spectrum shift in time sequence could be used to determine dynamic strain information at a specific position of the vibrated state with respect to that of the non-vibrated state. Measurable frequency range of 0-32 Hz with the spatial resolution of 10 cm is demonstrated along a 17 m fiber.

Qin, Zengguang

2013-01-01

416

Radiation fields backscattered from material interfaces: I. Biological effectiveness.  

PubMed

Confluent cultures of CHO-K1 and CHO-xrs5 cells were irradiated attached to 6 microm Mylar with 137Cs gamma rays and 200 kVp X rays adjacent to scattering materials consisting of polystyrene, glass, aluminum, copper, tin and lead. The absorbed dose in cell nuclei was estimated from measurements of backscattered dose made with a parallel-plate ion chamber with a 5-microm Mylar window and a gas volume whose thickness was equivalent to approximately 2.6 microm of cells or tissue. Cell inactivation after various doses was measured by clonogenic assays after trypsinization and enumeration. Survival curves constructed from data pooled from at least two independent experiments were best fitted to a linear-quadratic (LQ) or a linear equation for CHO-K1 and CHO-xrs5 cells, respectively. An average distance of 9.3+/-1.9 microm from the scattering surfaces to the midline of nuclei for both the cell lines was estimated from electron micrographs of fixed cell sections. The major differences in biological effect observed when the cells were irradiated adjacent to these materials could be largely explained by the differences in the physical dose. Further analyses using the LQ equation suggested additional biological effects with implications for the mechanisms involved. CHO-K1 cells showed a small but consistent increase in the low-dose (alpha-inactivation coefficient) mechanism for both radiations scattered from high-Z material. An increased value of the alpha coefficient suggests an increase in RBE which could be associated with a higher proportion of low-energy and track-end electrons in these fields. The radiation fields which produced maximum single-hit killing in CHO-K1 cells also produced less killing by the quadratic (beta-inactivation coefficient) mechanism. In contrast, when similarly irradiated, CHO-xrs5 cells exhibited significantly lower alpha coefficients of inactivation. The mechanistic basis for this opposite effect of backscattered radiations in these cell lines is as yet unknown. PMID:9768854

Zellmer, D L; Chapman, J D; Stobbe, C C; Xu, F; Das, I J

1998-10-01

417

Characterization of microstructure with low frequency electromagnetic techniques  

SciTech Connect

A new computational method for characterizing the relationship between surface crystallography and electrical conductivity in anisotropic materials with low frequency electromagnetic techniques is presented. The method is discussed from the standpoint of characterizing the orientation of a single grain, as well as characterizing statistical information about grain ensembles in the microstructure. Large-area electron backscatter diffraction (EBSD) data was obtained and used in conjunction with a synthetic aperture approach to simulate the eddy current response of beta annealed Ti-6Al-4V. Experimental eddy current results are compared to the computed eddy current approximations based on electron backscatter diffraction (EBSD) data, demonstrating good agreement. The detectability of notches in the presence of noise from microstructure is analyzed with the described simulation method and advantages and limitations of this method are discussed relative to other NDE techniques for such analysis.

Cherry, Matthew R.; Sathish, Shamachary [University of Dayton Research Institute, Structural Integrity Division, 300 College Park, Dayton, OH 45469-0020 (United States); Pilchak, Adam L.; Blodgett, Mark P. [Air Force Research Laboratory, Materials and Manufacturing Directorate (AFRL/RXCM), 2230 10th St., WPAFB, OH 45433 (United States); Cherry, Aaron J. [Southwest Ohio Council for Higher Education, 3155 Research Blvd., Suite 204, Dayton, OH 45420-4015 (United States)

2014-02-18

418

Temporal filtering by double diffraction.  

PubMed

We present a theoretical analysis of the temporal behavior of double-diffraction setups. It applies, in particular, to Talbot and Montgomery interferometers, whose operation is based on the self-imaging effect. The use of both types of interferometer as temporal filters for optical and terahertz applications was recently suggested. We show that double-diffraction setups can be modeled as communications channels with dispersive behavior caused by diffraction. We develop mathematical expressions for the phase delay, the group velocity, and the group-velocity dispersion for both quasi-monochromatic and polychromatic case. Based on these results, the temporal impulse response of a double-diffraction setup is derived. Finally, a general description of its practical implementation are presented. PMID:15298406

Jahns, Jürgen; Lohmann, Adolf W

2004-08-01

419

Electrically-programmable diffraction grating  

DOEpatents

An electrically-programmable diffraction grating is disclosed. The programmable grating includes a substrate having a plurality of electrodes formed thereon and a moveable grating element above each of the electrodes. The grating elements are electrostatically programmable to form a diffraction grating for diffracting an incident beam of light as it is reflected from the upper surfaces of the grating elements. The programmable diffraction grating, formed by a micromachining process, has applications for optical information processing (e.g. optical correlators and computers), for multiplexing and demultiplexing a plurality of light beams of different wavelengths (e.g. for optical fiber communications), and for forming spectrometers (e.g. correlation and scanning spectrometers). 14 figs.

Ricco, A.J.; Butler, M.A.; Sinclair, M.B.; Senturia, S.D.

1998-05-26

420

X-Ray Diffraction Apparatus  

NASA Technical Reports Server (NTRS)

An x-ray diffraction apparatus for use in analyzing the x-ray diffraction pattern of a sample is introduced. The apparatus includes a beam source for generating a collimated x-ray beam having one or more discrete x-ray energies, a holder for holding the sample to be analyzed in the path of the beam, and a charge-coupled device having an array of pixels for detecting, in one or more selected photon energy ranges, x-ray diffraction photons produced by irradiating such a sample with said beam. The CCD is coupled to an output unit which receives input information relating to the energies of photons striking each pixel in the CCD, and constructs the diffraction pattern of photons within a selected energy range striking the CCD.

Blake, David F. (Inventor); Bryson, Charles (Inventor); Freund, Friedmann (Inventor)

1996-01-01

421

Pinwheel patterns and powder diffraction  

E-print Network

Pinwheel patterns and their higher dimensional generalisations display continuous circular or spherical symmetries in spite of being perfectly ordered. The same symmetries show up in the corresponding diffraction images. Interestingly, they also arise from amorphous systems, and also from regular crystals when investigated by powder diffraction. We present first steps and results towards a general frame to investigate such systems, with emphasis on statistical properties that are helpful to understand and compare the diffraction images. We concentrate on properties that are accessible via an alternative substitution rule for the pinwheel tiling, based on two different prototiles. Due to striking similarities, we compare our results with the toy model for the powder diffraction of the square lattice.

Michael Baake; Dirk Frettlöh; Uwe Grimm

2006-10-06

422

1. Diffraction and the X-Ray Powder Diffractometer . . . . . . . . 1 1.1 Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  

E-print Network

Contents 1. Diffraction and the X-Ray Powder Diffractometer . . . . . . . . 1 1.1 Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.1 Introduction to Diffraction . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1.2 Bragg Diffraction . . . . . . . . . . . . . . . . . 25 1.3.3 Monochromators, Filters, Mirrors

423

Computer simulation of a backscattered x-ray fluorescence system.  

PubMed

An EGSnrc user code is developed to simulate a backscattered geometry in vivo x-ray fluorescence system for the measurement of platinum concentration in head and neck tumours. The user code is fundamentally based on a previous study which used the EGS4 Monte Carlo code. The new user code, which we have developed in this study, has new improvements which made it able to simulate the process of photon transportation through the different components of the modelled x-ray fluorescence system. The simulation process included modelling of the photon source, collimators, phantoms and detector. Simulation results were compared and evaluated against x-ray fluorescence data obtained experimentally from an existing system developed by the Swansea In vivo Analysis and Cancer Research Group. In addition, simulation results of this study were also compared with our previous study in which the EGS4 user code was used. Comparison between results has shown that the new EGSnrc user code was able to reproduce the spectral shape obtained using the experimental x-ray fluorescence system. The area under the Compton peak differs by 2.5% between the experimental measurement and the EGSnrc simulation. Similarly, the area under the two Pt K? peaks differs by 2.3% and 2.2%. PMID:25567407

Al-Ghorabie, Fayez H H

2015-01-01

424

Microwave backscattering and emission model for grass canopies  

NASA Technical Reports Server (NTRS)

Microwave radar and radiometer measurements of grasslands indicate a substantial reduction in sensor sensitivity to soil moisture in the presence of a thatch layer. When this layer is wet it masks changes in the underlying soil, making the canopy appear warm in the case of passive sensors (radiometer) and decreasing backscatter in the active case (scatterometer). A model for a grass canopy with thatch will be presented in this paper to explain this behavior and to compare with observations. The canopy model consists of three layers: grass, thatch, and the underlying soil. The grass blades are modeled by elongated elliptical discs and the thatch is modeled as a collection of disk shaped water droplets (i.e., the dry matter is neglected). The ground is homogeneous and flat. The distorted Born approximation is used to compute the radar cross section of this three layer canopy and the emissivity is computed from the radar cross section using the Peake formulation for the passive problem. Results are computed at L-band (1.4 GHz) and C-band (4.75 GHz) using canopy parameters (i.e., plant geometry, soil moisture, plant moisture, etc.) representative of Konza Prairie grasslands. The results are compared to C-band scatterometer measurements and L-band radiometer measurements at these grasslands.

Saatchi, Sasan S.; Levine, David M.; Lang, Roger H.

1994-01-01

425

Anomalous radar backscatter from Titan’s surface?  

NASA Astrophysics Data System (ADS)

Since Cassini arrived at Saturn in 2004, its moon Titan has been thoroughly mapped by the RADAR instrument at 2-cm wavelength, in both active and passive modes. Some regions on Titan, including Xanadu and various bright hummocky bright terrains, contain surfaces that are among the most radar-bright encountered in the Solar System. This high brightness has been generally attributed to volume scattering processes in the inhomogeneous, low-loss medium expected for a cold, icy satellite surface. We can test this assumption now that the emissivity has been obtained from the concurrent radiometric measurements for nearly all the surface, with unprecedented accuracy (Janssen et al., and the Cassini RADAR Team [2009]. Icarus 200, 222-239). Kirchhoff’s law of thermal radiation relates the radar and radiometric properties in a way that has never been fully exploited. In this paper we examine here how this law may be applied in this case to better understand the nature of Titan’s radar-bright regions. We develop a quantitative model that, when compared to the observational data, allows us to conclude that either the reflective characteristics of the putative volume scattering subsurface must be highly constrained, or, more likely, organized structure on or in the surface is present that enhances the backscatter.

Janssen, M. A.; Le Gall, A.; Wye, L. C.

2011-03-01

426

Observations of Enhanced Radar Backscatter (ERB) from Millstone Hill  

NASA Technical Reports Server (NTRS)

Intense enhancements of the incoherent radar backscatter spectrum from the topside ionosphere were observed with the Millstone Hill UHF radar. Enhancements occurring at the local ion acoustic frequency causing large asymmetries in the measured ion line may be produced by current driven instabilities. These enhancements pose a practical problem for space surveillance systems because their cross section and spectral width are characteristic of satellites. Conversely, their hard target signature complicates the study of naturally occurring ERB events; it is nearly impossible to distinguish them from satellites based on a single measurement. Statistical comparisons of observed coherent echo distributions with predictions from a satellite catalog were used to broadly identify periods of ERB activity. A series of experiments using multiple diagnostics, including satellite instruments, for simultaneous observations have established the association of ERB with large fluxes of soft suprathermal electrons carrying field aligned currents. Zenith data are also presented which show the asymmetric growth of ion acoustic waves directly above Millstone Hill. Details of these results are presented.

Lee, M. C.

1991-01-01

427

Verification measurement of a polarization Raman elastic-backscatter lidar  

NASA Technical Reports Server (NTRS)

By measuring the depolarization of light Raman scattered from a gas of known number density (nitrogen), it is possible to determine the influence of multiple scattering on lidar signals. In order to realize such measurements, linearly polarized laser light is emitted and two components of the nitrogen Raman signals, with E vectors parallel (parallel P sub lambda R) and perpendicular (perpendicular P sub lambda R) to the plane of polarization of the laser light, are measured. The depolarization ratio, delta sub lambda R = perpendicular P sub lambda R/parallel P sub lambda R, is constant if only the Raman scattering process contributes to the signal. Any variation of the depolarization is caused by additional elastic, and, thus, multiple scattering. If the contribution of multiple scattered light to the lidar signals is known, other parameters determined with the systems such as extinction, backscattering, and the depolarization of elastically scattered light, can be corrected for this influence. The lidar system used for the polarization measurements, especially the receiver setup, is described. The calibration of the apparatus and a clear air measurement are discussed.

Schulze, Christoph; Wandinger, Ulla; Ansmann, Albert; Weitkamp, Claus; Michaelis, Walfried

1992-01-01

428

Improvement of sensitivity in high-resolution Rutherford backscattering spectroscopy  

SciTech Connect

The sensitivity (limit of detection) of high-resolution Rutherford backscattering spectroscopy (HRBS) is mainly determined by the background noise of the spectrometer. There are two major origins of the background noise in HRBS, one is the stray ions scattered from the inner wall of the vacuum chamber of the spectrometer and the other is the dark noise of the microchannel plate (MCP) detector which is commonly used as a focal plane detector of the spectrometer in HRBS. In order to reject the stray ions, several barriers are installed inside the spectrometer and a thin Mylar foil is mounted in front of the detector. The dark noise of the MCP detector is rejected by the coincidence measurement with the secondary electrons emitted from the Mylar foil upon the ion passage. After these improvements, the background noise is reduced by a factor of 200 at a maximum. The detection limit can be improved down to 10 ppm for As in Si at a measurement time of 1 h under ideal conditions.

Hashimoto, H.; Nakajima, K.; Suzuki, M.; Kimura, K. [Department of Micro Engineering, Kyoto University, Kyoto 606-8501 (Japan); Sasakawa, K. [Department of Micro Engineering, Kyoto University, Kyoto 606-8501 (Japan); Kobelco Research Institute, Inc., Takatsukadai 1-5-5, Nishi-ku, Kobe 651-2271 (Japan)

2011-06-15

429

Modeling the backscattering and transmission properties of vegetation canopies  

NASA Technical Reports Server (NTRS)

Experimental measurements of canopy attenuation at 10.2 GHz (X-band) for canopies of wheat and soybeans, experimental observations of the effect upon the microwave backscattering coefficient (sigma) of free water in a vegetation canopy, and experimental measurements of sigma (10.2 GHz, 50 deg, VV and VH polarization) of 30 agricultural fields over the growing season of each crop are discussed. The measurements of the canopy attenuation through wheat independently determined the attenuation resulting from the wheat heads and that from the stalks. An experiment conducted to simulate the effects of rain or dew on sigma showed that sigma increases by about 3 dB as a result of spraying a vegetation canopy with water. The temporal observations of sigma for the 30 agricultural fields (10 each of wheat, corn, and soybeans) indicated fields of the same crop type exhibits similar temporal patterns. Models previously reported were tested using these multitemporal sigma data, and a new model for each crop type was developed and tested. The new models proved to be superior to the previous ones.

Allen, C. T.; Ulaby, F. T.

1984-01-01

430

Ray-Based Calculations of Backscatter in Laser Fusion Targets  

SciTech Connect

A steady-state model for Brillouin and Raman backscatter along a laser ray path is presented. The daughter plasma waves are treated in the strong damping limit, and have amplitudes given by the (linear) kinetic response to the ponderomotive drive. Pump depletion, inverse-bremsstrahlung damping, bremsstrahlung emission, Thomson scattering off density fluctuations, and whole-beam focusing are included. The numerical code deplete, which implements this model, is described. The model is compared with traditional linear gain calculations, as well as 'plane-wave' simulations with the paraxial propagation code pf3d. Comparisons with Brillouin-scattering experiments at the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, p. 495 (1997)] show that laser speckles greatly enhance the reflectivity over the deplete results. An approximate upper bound on this enhancement, motivated by phase conjugation, is given by doubling the deplete coupling coefficient. Analysis with deplete of an ignition design for the National Ignition Facility (NIF) [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Technol. 26, p. 755 (1994)], with a peak radiation temperature of 285 eV, shows encouragingly low reflectivity. Doubling the coupling to bound the speckle enhancement suggests a less optimistic picture. Re-absorption of Raman light is seen to be significant in this design.

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

2008-02-26

431

Optimizing the Rutherford Backscattering Spectrometry setup in a nuclear microprobe  

NASA Astrophysics Data System (ADS)

Rutherford Backscattering Spectrometry (RBS) as one of the standard techniques of ion beam analysis for non-destructive quantification of film thicknesses and elemental concentrations, in general requires a good mass separation and energy resolution. In nuclear microprobes large solid angles of detection of ?100 msr are necessary to compensate for the comparably low beam current. However, under these conditions geometrical straggling effects cannot be neglected anymore. Therefore, in order to optimize the RBS detection setup, the geometrical straggling was calculated for circular detectors and the noise contributions to the signal generation and amplification analyzed. The analysis shows that an annular RBS detector should be used directly connected to a dedicated in-vacuum preamplifier. In this way, as is demonstrated in this study with preamplifiers based on an Amptek A250 in a very compact, reliable and low-cost package, excellent energy resolutions of (10.6 ± 0.2) keV FWHM can be achieved in 2.29 MeV proton RBS for a 300 mm2 Canberra PIPS detector mounted under 86 msr solid angle. For smaller detectors even better energy resolutions are obtained, i.e. (5.1 ± 0.2) keV for a 50 mm2 Canberra PIPS and (5.8 ± 0.2) keV for a Hamamatsu S1223-01 PIN-photodiode detector for 2.29 MeV proton RBS and Scanning Transmission Ion Microscopy, respectively.

Klingner, N.; Vogt, J.; Spemann, D.

2013-07-01

432

Vacuum birefringence by Compton backscattering through a strong field  

NASA Astrophysics Data System (ADS)

We propose a novel scheme to measure nonlinear effects in electrodynamics arising from QED corrections. Our theoretical starting point is the Heisenberg-Euler-Schwinger effective Lagrangian which predicts that a vacuum with a strong static electromagnetic field turns birefringent. We propose to employ a pulsed laser to create Compton backscattered photons off a high energy electron beam. These photons will pass through a strong static magnetic field, which according to the QED prediction changes the state of polarization of the radiation—an effect proportional to the photon energy. This change will be measured by using an aligned single crystal, since a large difference in the pair production cross sections at high energies can be achieved with proper orientation of the crystal. As an example we will consider the machine, LHeC, under consideration at CERN as the source of these electrons, and an LHC dipole magnet as the source of the strong static magnetic field. In the proposed experimental setup the birefringence effect will be manifested in a difference in the number of pairs created in the polarizer crystal as the initial laser light has a varying state of polarization, achieved with a rotating quarter wave plate. This will be seen as a clear peak in the Fourier transform spectrum of the pair-production rate signal, which can be obtained with 3 hours of measurement. We also comment on the sensitivity of the experiment, to the existence of an axion, a hypothetical spin-0 particle that couples to two photons.

Wistisen, Tobias N.; Uggerhøj, Ulrik I.

2013-09-01

433

Damage in silicon carbide induced by Rutherford backscattering analysis  

NASA Astrophysics Data System (ADS)

Damage in silicon carbide generated by ion implantation or irradiation is usually analyzed by Rutherford backscattering spectroscopy in combination with channeling (RBS/C) of MeV He + ions, a technique which is considered to be largely non-destructive. In this paper we report on swelling of 6H-SiC induced by He + implantation at doses commensurate with, or lower than those commonly used for obtaining RBS/C spectra of desirable statistics. The swelling increases by about 40% if the He + ions are implanted in a non-channeling direction. The formation of high concentrations of deep-reaching (?m range) defects due to RBS/C is confirmed by slow positron implantation spectroscopy (SPIS) measurements. An optical damage depth-profile, with distinct optical properties corresponding to the regions of electronic and nuclear stopping, is obtained from a fit to polarized infrared reflection spectroscopy (PIRR) data and compared to TRIM calculation. Auger electron spectroscopy (AES) shows that the specific color of the implanted area is not due to the deposition of a thin surface film during He + implantation, and the swelling is not related to chemical reactions in the near-surface region. The formation of additional disorder from RBS/C may corrupt the respective data obtained subsequently by SPIS and PIRR. Therefore, RBS/C measurements should always be carried out last, i.e. following analytical techniques which are certainly non-destructive.

Fukarek, W.; Yankov, R. A.; Anwand, W.; Heera, V.

1998-08-01

434

Investigation of radar backscattering from second-year sea ice  

NASA Technical Reports Server (NTRS)

The scattering properties of second-year ice were studied in an experiment at Mould Bay in April 1983. Radar backscattering measurements were made at frequencies of 5.2, 9.6, 13.6, and 16.6 GHz for vertical polarization, horizontal polarization and cross polarizations, with incidence angles ranging from 15 to 70 deg. The results indicate that the second-year ice scattering characteristics were different from first-year ice and also different from multiyear ice. The fading properties of radar signals were studied and compared with experimental data. The influence of snow cover on sea ice can be evaluated by accounting for the increase in the number of independent samples from snow volume with respect to that for bare ice surface. A technique for calculating the snow depth was established by this principle and a reasonable agreement has been observed. It appears that this is a usable way to measure depth in snow or other snow-like media using radar.

Lei, Guang-Tsai; Moore, Richard K.; Gogineni, S. P.

1988-01-01

435

Coherent backscatter radar imaging in Brazil: Bottomside radar plumes  

NASA Astrophysics Data System (ADS)

The 30 MHz coherent scatter backscatter radar in Sao Luis, Brazil has been used for routine two-antenna observations of equatorial E and F region field aligned irregularities since 2002. In 2005, two antenna modules were added to the already existing two modules. These new modules would allow observations with 6 independent interferometric baselines, which then could be used for construction of in-beam radar images similar to those produced at Jicamarca Radio Observatory [e.g. Hysell, 1996]. Despite the low transmitting power and reduced number of baselines, in-beam radar images of F-region scattering structures were successfully constructed with the Sao Luis radar observations. Initial imaging results were used to investigate the horizontal structure of a bottom-type scattering that preceded a fully developed radar plume [Rodrigues et al., 2009]. Here, we examine Sao Luis observations of bottomside radar plumes. Details of the observations and analysis will be presented and the characteristics of the scattering structures seen with this radar will be discussed.

Rodrigues, F. S.; de Paula, E. R.; Hysell, D. L.

2010-12-01

436

DIFFRACTION MODELING FOR INTERACTIVE VIRTUAL ACOUSTICAL ENVIRONMENTS  

E-print Network

DIFFRACTION MODELING FOR INTERACTIVE VIRTUAL ACOUSTICAL ENVIRONMENTS Bill Kapralos Faculty. eem@cs.dal.ca Keywords: Sonel mapping, acoustical diffraction modeling, virtual environments Abstract of mag- nitude of the wavelength of audible sounds, diffraction is an elementary means of sound

Jenkin, Michael R. M.

437

Very low grazing angle radar backscatter from the ocean surface  

Microsoft Academic Search

A very low grazing angle (<0.2°) sea clutter measurements program was conducted with the L- and S-band TRADEX and C-band ALCOR radars on Roi Namur, Marshall Islands. Clutter returns were observed to the maximum measurement range of 60 km. L -band data could be explained by diffraction over a spherical Earth, but at the higher frequencies ducting was in clear

Henry H. Helmken; Matthew J. Vanderhill

1990-01-01

438

Adaptive Concentration Control of Cooling and Antisolvent Crystallization with Laser Backscattering Measurement  

E-print Network

Adaptive Concentration Control of Cooling and Antisolvent Crystallization with Laser Backscattering implements the temperature or antisolvent addition rate versus time. An adaptive concentration control, becomes increasingly important.6-8 One method for operating a pharmaceutical crystallization process

Braatz, Richard D.

439

General view looking northnortheast at antenna array OvertheHorizon Backscatter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view looking north-northeast at antenna array - Over-the-Horizon Backscatter Radar Network, Moscow Radar Site Transmit Sector Two Antenna Array, At the end of Steam Road, Moscow, Somerset County, ME

440

Detail of antenna array, looking northnorthwest OvertheHorizon Backscatter Radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of antenna array, looking north-northwest - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Five Antenna Array, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

441

General view of Antenna Array, looking west OvertheHorizon Backscatter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view of Antenna Array, looking west - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Six Antenna Array, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

442

General view looking northnortheast at antenna array OvertheHorizon Backscatter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view looking north-northeast at antenna array - Over-the-Horizon Backscatter Radar Network, Moscow Radar Site Transmit Sector One Antenna Array, At the end of Steam Road, Moscow, Somerset County, ME

443

Detail of antenna tower structure, looking northnorthwest OvertheHorizon Backscatter ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of antenna tower structure, looking north-northwest - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Five Antenna Array, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

444

Exterior view, looking west OvertheHorizon Backscatter Radar Network, Tulelake ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Exterior view, looking west - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Four Receiver Building, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

445

Exterior view, looking southwest OvertheHorizon Backscatter Radar Network, Tulelake ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Exterior view, looking southwest - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Four Receiver Building, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

446

Interior view, looking northwest OvertheHorizon Backscatter Radar Network, Tulelake ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior view, looking northwest - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Four Receiver Building, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

447

General view of array, looking northeast OvertheHorizon Backscatter Radar ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view of array, looking northeast - Over-the-Horizon Backscatter Radar Network, Tulelake Radar Site Receive Sector Four Antenna Array, Unnamed Road West of Double Head Road, Tulelake, Siskiyou County, CA

448

A pulsed-laser calibration system for the laser backscatter diagnostics at the Omega laser  

SciTech Connect

A calibration system has been developed that allows a direct determination of the sensitivity of the laser backscatter diagnostics at the Omega laser. A motorized mirror at the target location redirects individual pulses of a millijoule-class laser onto the diagnostic to allow the in situ measurement of the local point response of the backscatter diagnostics. Featuring dual wavelength capability at the second and third harmonics of the Nd:YAG laser, both spectral channels of the backscatter diagnostics can be directly calibrated. In addition, channel cross-talk and polarization sensitivity can be determined. The calibration system has been employed repeatedly over the last two years and has enabled precise backscatter measurements of both stimulated Brillouin scattering and stimulated Raman scattering in gas-filled Hohlraum targets that emulate conditions relevant to those in inertial confinement fusion targets.

Neumayer, Paul; Sorce, Charles; Froula, Dustin H.; Divol, Laurent; Rekow, Vern; Loughman, Kevin; Knight, Russel; Glenzer, Siegfried H. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Bahr, Raymond; Seka, Wolf [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299 (United States)

2008-10-15

449

Studying Clouds and Aerosols with Lidar Depolarization Ratio and Backscatter Relationships  

E-print Network

properties of clouds and aerosols. The relationships between depolarization ratio and backscatter allow us to retrieve particle thermodynamic phase and shape and/or orientation of aerosols and clouds. The first part is devoted to the investigation...

Cho, Hyoun-Myoung

2012-02-14

450

Oblique view to south OvertheHorizon Backscatter Radar Network, Mountain ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Oblique view to south - Over-the-Horizon Backscatter Radar Network, Mountain Home Air Force Operations Building, On Desert Street at 9th Avenue Mountain Home Air Force Base, Mountain Home, Elmore County, ID

451

Enhanced Doppler Effect in the Upper Hybrid Resonance Microwave Backscattering Experiment  

E-print Network

Enhanced Doppler Effect in the Upper Hybrid Resonance Microwave Backscattering Experiment A, Politekhnicheskaya 26, 194021 St.Petersburg, Russia Observations of enhanced Doppler frequency shift effect based on this effect is proposed. 1. INTRODUCTION Investigation of tokamak plasma poloidal rotation

Paris-Sud XI, Université de

452

Correction of Doppler-broadened Rayleigh backscattering effects in H2O dial measurements  

NASA Technical Reports Server (NTRS)

A general method of solutions for treating effects of Doppler-broadened Rayleigh backscattering in H2O Differential Absorption Lidar (DIAL) measurements are described and discussed. Errors in vertical DIAL measuremtns caused by this laser line broadening effect can be very large and, therfore, this effect has to be accounted for accurately. To analyze and correct effects of Doppler-broadened Rayleigh backscattering in DIAL experiments, a generalized DIAL approximation was derived starting from a lidar equation, which includes Doppler broadening. To evaluate the accuracy of H2O DIAL measurements, computer simulations were performed. It was concluded that correction of Doppler broadened Rayleigh backscattering is possible with good accuracy in most cases of tropospheric H2O DIAL measurements, but great care has to be taken when layers with steep gradients of Mie backscattering like clouds or inversion layers are present.

Ansmann, A.; Bosenberg, J.

1986-01-01

453

Southern Hemisphere tropospheric aerosol backscatter measurements - Implications for a laser wind system  

NASA Astrophysics Data System (ADS)

To identify the aerosol size fraction that is responsible for the 10.6-micron backscatter and the morphological composition of these particles, values of backscatter coefficient at 0.532 micron, 0.694 micron, and 10.6 microns were determined both by direct measurement and by Mie computation from measured microphysical properties of aerosols over eastern Australia between 4 deg and 41 deg S. The values of backscatter coefficient determined from direct measurements at 10.6 microns were found to agree well with values obtained indirectly from calculations based on measured aerosol particle size distributions and properties. It was also found that backscatter at 10.6 microns and at visible wavelengths were sensitive to different regions of the aerosol size spectrum, with considerable day-to-day variability observed at all wavelengths.

Gras, J. L.; Platt, C. M. R.; Young, S. A.; Jones, W. D.; Huffaker, R. M.

1991-03-01

454

Characterization of nuclear physics targets using Rutherford backscattering and particle induced x-ray emission  

E-print Network

Rutherford backscattering and particle induced x-ray emission have been utilized to precisely characterize targets used in nuclear fission experiments. The method allows for a fast and non destructive determination of target thickness, homogeneity and element composition.

Th. Rubehn; G. J. Wozniak; L. Phair; L. G. Moretto; Kin M. Yu

1996-09-23

455

Geomorphology, acoustic backscatter, and processes in Santa Monica Bay from multibeam  

E-print Network

, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gra- dients Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers: Geomorphology; Submarine canyons; Multibeam; Backscatter; California borderland Marine Environmental Research 56

New Hampshire, University of

456

ERS-1 SAR backscatter changes associated with ice growing on shallow lakes in Arctic Alaska  

NASA Technical Reports Server (NTRS)

Spatial and temporal backscatter intensity (sigma(sup o)) variations from ice growing on shallow lakes during winter 1991-92 near Barrow, NW Alaska, have been quantified for the first time using ERS-I C-band SAR data acquired at the Alaska SAR Facility. A field and laboratory validation program, including measurements of the thickness and structure-stratigraphy of the ice, indicates that sigma(sup o) values are strongly dependent on whether the ice freezes to the lake bottom, or remains afloat. Backscatter intensity decreases significantly when the ice grounds on the bottom. Strong backscatter from floating ice is attributed to a specular ice-water interface and vertically oriented tubular bubbles. During the spring thaw, backscatter undergoes a reversal; sigma(sup o) values from ice that was grounded increase, while sigma(sup o) values from ice that was afloat decrease. This phenomenon has not previously been reported.

Jeffries, M. O.; Wakabayashi, H.; Weeks, W. F.

1993-01-01

457

High frequency acoustic backscattering enhancements for finite cylindrical shells in water at oblique incidence  

NASA Astrophysics Data System (ADS)

The scattering of sound by finite cylindrical shells in water is investigated. Both experimental and theoretical examinations are performed which include comparisons of measured backscattering enhancements with a quantitative ray theory and an approximate partial wave series solution. Broadband backscattering experiments are carried out for the full range of tilt angles (measured with respect to the cylinder's axis) to identify regions of enhanced backscattering from moderately thick-walled steel cylindrical shells (having thickness-to-radius ratios of 7.6% and 16.3%). It is found that the backscattering is significantly enhanced when conditions arise such that a generalization of a leaky Lamb wave is launched on the shell. This surface guided wave reflects off the shell truncation, which is flat and perpendicular to the cylinder axis, and reradiates into the backscattering direction. In addition to various helical ray contributions, particularly large enhancements are observed for a ray propagating along the cylinder's meridian. The meridional ray enhancement for the generalization of the lowest order antisymmetric leaky Lamb wave is observed over a large range of tilt angles, nearing end-on incidence in the coincidence frequency region. Coupling conditions are determined which locate the various enhancements in frequency-angle space. High- frequency narrowband backscattering experiments are used to make quantitative measurements of enhancement amplitudes, which agree well with theoretical predictions. For highly oblique tilt angles the meridional ray amplitudes are several times greater than the specular reflection amplitude for scattering from a rigid sphere of like radius. Both air-filled and water- filled cylindrical shells are examined. An abrupt drop in the backscattered meridional ray amplitude is observed at very high frequencies. This drop is the result of the next antisymmetric leaky Lamb mode and mode conversion upon reflection at the cylinder's end. Simplified calculations display aspects of this threshold behavior. In addition experimental procedures are described for obtaining transient and wide bandwidth backscattering data using a PVDF sheet source in water for frequencies extending up to 1 MHz.

Morse, Scot Franklin

458

Numerical simulation of low-grazing-angle ocean microwave backscatter and its relation to sea spikes  

Microsoft Academic Search

This paper presents the results of numerically simulating microwave backscatter from a deep-water breaking wave profile. Enhanced microwave backscatter from the crests of breaking waves has been hypothesized as the source of bright short-lived microwave radar echoes that are observed at low-grazing angles (LGAs). The characteristics of these “sea spikes” are distinctly different from the Bragg-scatter echoes that dominate measurements

Charles L. Rino; Hoc D. Ngo

1998-01-01

459

Backscattering of light from disklike particles: is fine-scale structure or gross morphology more important?  

PubMed

The backscattering of light from disklike objects possessing periodic structures (e.g., resembling a wheel with spokes, hereafter called a pinwheel) or an object with a wavelength-sized deviation from a flat disk (e.g., a spherical cap) has been computed by using the discrete dipole approximation. The disks ranged in diameter from 1.5 to 2.7 microm with thicknesses from 0.04 to 0.15 microm. The goal of the study was to obtain some understanding of the differences between the backscattering of a collection of such objects in random orientation and a collection of randomly oriented homogeneous disks of the same size, i.e., the conditions under which the gross morphology (e.g., disklikeness) of these objects determines their backscattering. The computations for pinwheels showed that their backscattering cross sections were nearly identical to those of homogeneous disks of similar size (but with reduced effective refractive indices that are easily estimated) as long as the maximum separations between the spokes was less than one quarter of the wavelength. In this regime the backscattering is totally governed by the particle's gross morphology and effective index. For larger spoke separation, departures from a homogeneous disk are observed and manifest as significant increases (many times) in backscattering. In the case of spherical caps with the same projected area as the associated disk, the computations again show a complete similarity in their backscattering, and when the disks are sufficiently thin (with thickness divided by wavelength<0.15 to 0.25) there is very little difference between the backscattering of a cap and the associated disk. PMID:16946797

Gordon, Howard R

2006-09-20

460

Unusual Radar Backscatter Properties Along the Northern Rim of Imbrium Basin  

NASA Technical Reports Server (NTRS)

In general, radar backscatter from the lunar terrae is 2-4 times that of the maria. One exception to this is the terra terrain along the northern rim of Imbrium Basin. The highlands that surround Sinus Iridum and crater Plato have long-wavelength (70-cm) radar backscatter that is comparable to or lower than that from the adjacent maria. We are studying new 70-cm radar images and earlier multispectral data to better constrain the regional geology.

Thompson, T. W.; Campbell, Bruce A.

2005-01-01

461

Influence of cell packing by centrifugation on 40MHz ultrasound backscatter  

Microsoft Academic Search

High-frequency ultrasound (HFUS) signals backscattered from RBL-2H3 cell pellets prepared under different centrifugal forces were analyzed to investigate the packing effect of cell aggregates. The measurements were performed in a pulse-echo setup with a 40-MHz transducer. The changes of ultrasound signals from cell pellet in backscattered power, statistical parameter, and pellet thickness were monitored after centrifugation at between 100g and

Kweon-Ho Nam; Min Joo Choi; Eun Sook Yoo; Dong-Guk Paeng

2011-01-01

462

Backscattering of light from disklike particles: is fine-scale structure or gross morphology more important?  

NASA Astrophysics Data System (ADS)

The backscattering of light from disklike objects possessing periodic structures (e.g., resembling a wheel with spokes, hereafter called a pinwheel) or an object with a wavelength-sized deviation from a flat disk (e.g., a spherical cap) has been computed by using the discrete dipole approximation. The disks ranged in diameter from 1.5 to 2.7 ?m with thicknesses from 0.04 to 0.15 ?m. The goal of the study was to obtain some understanding of the differences between the backscattering of a collection of such objects in random orientation and a collection of randomly oriented homogeneous disks of the same size, i.e., the conditions under which the gross morphology (e.g., disklikeness) of these objects determines their backscattering. The computations for pinwheels showed that their backscattering cross sections were nearly identical to those of homogeneous disks of similar size (but with reduced effective refractive indices that are easily estimated) as long as the maximum separations between the spokes was less than one quarter of the wavelength. In this regime the backscattering is totally governed by the particle's gross morphology and effective index. For larger spoke separation, departures from a homogeneous disk are observed and manifest as significant increases (many times) in backscattering. In the case of spherical caps with the same projected area as the associated disk, the computations again show a complete similarity in their backscattering, and when the disks are sufficiently thin (with thickness divided by wavelength <0.15 to 0.25) there is very little difference between the backscattering of a cap and the associated disk.

Gordon, Howard R.

2006-09-01

463

Measurement of multiple scattering effects with a polarization Raman elastic-backscatter lidar  

NASA Technical Reports Server (NTRS)

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 scattered from nitrogen molecules. With this technique the depolarization effect due to multiple scattering can be separated from single scattering polarization. Presented here are a short discussion of the idea and a measurement example.

Wandinge