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Title: A Wide-Beam X-ray Source Suitable for Diffraction Enhanced Imaging Applications

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Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Instruments and Methods A; Journal Volume: 566; Journal Issue: 2
Country of Publication:
United States
national synchrotron light source

Citation Formats

Kim,C., Bourham, M., and Doster, J. A Wide-Beam X-ray Source Suitable for Diffraction Enhanced Imaging Applications. United States: N. p., 2006. Web. doi:10.1016/j.nima.2006.07.041.
Kim,C., Bourham, M., & Doster, J. A Wide-Beam X-ray Source Suitable for Diffraction Enhanced Imaging Applications. United States. doi:10.1016/j.nima.2006.07.041.
Kim,C., Bourham, M., and Doster, J. Sun . "A Wide-Beam X-ray Source Suitable for Diffraction Enhanced Imaging Applications". United States. doi:10.1016/j.nima.2006.07.041.
title = {A Wide-Beam X-ray Source Suitable for Diffraction Enhanced Imaging Applications},
author = {Kim,C. and Bourham, M. and Doster, J.},
abstractNote = {},
doi = {10.1016/j.nima.2006.07.041},
journal = {Nuclear Instruments and Methods A},
number = 2,
volume = 566,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
  • The X-ray Diffraction Enhanced Imaging (DEI) is the analyzer-based X-ray imaging technique which allows extraction of the 'pure refraction' and 'apparent absorption' contrasts from two images taken on the opposite sides of the rocking curve of the analyzing crystal. The refraction contrast obtained by this method shows many advantages over conventional absorption contrast. It was successfully applied in medicine, technique and other fields of science. However, information provided by the method is rather qualitative than quantitative. This happens because either side of the rocking curve of the analyzer is approximated as a straight line what limits the ranges of applicabilitymore » and introduces additional error. One can easily overcome this problem considering the rocking curve as is instead of it's Taylor's expansion. This report is dedicated to the application of this idea in medical imaging and especially computed tomography based on the refraction contrast. The results obtained via both methods are presented and compared.« less
  • For detailed biomedical observations using the optimum phase-contrast x-ray imaging, quantitative comparisons of imaging performances of two major imaging methods--x-ray interferometric imaging (XII) and diffraction enhanced imaging (DEI)--were performed. Density sensitivity and spatial resolution of each imaging method were evaluated using phantom tomograms obtained by each method with the same x-ray dosage. For practical comparison of the methods, biological samples were also observed under the same conditions. The results show that XII has a higher sensitivity than that of DEI and is thus suitable for observation of soft biological tissues. On the other hand, DEI has a wider dynamic rangemore » of density and is thus suitable for observation of samples with large differences in density of different regions.« less
  • A review is presented of recent research into imaging on different length scales of defect structures in wide band gap semiconductors. This includes: synchrotron white beam X-ray topography (SWBXT) imaging of defects in SiC wafers and epilayers; high-resolution X-ray diffraction (HRXRD) and high-resolution transmission electron microscopy (HRTEM) studies of strain relaxation in AlN and GaN epilayers on on-axis and vicinal SiC and sapphire substrates; TEM studies of fault structures in GaN/AlN films on SiC substrates; and TEM studies of threading dislocation density reduction driven by growth mode modification in AlN films grown on sapphire substrates. In detail, studies of closed-coremore » and hollow-core screw dislocations, basal plane dislocations and stacking faults (SFs) in 4H- and 6H-SiC substrates and films are presented. The mechanism of improved mismatch strain relaxation associated with the growth of GaN (AlN) films on vicinal substrates is discussed. This is attributed to the combined effects of mutual tilt between the epilayer and the substrate, which helps to relax out-of-plane mismatch, and by the generation of geometric partial misfit dislocations (GPMDs), which serves both to relax in-plane mismatch and accommodate stacking differences between the epilayer and substrate at some proportion of the steps at the substrate/film interface. In addition, the formation mechanisms of intersecting SF structures observed in GaN/AlN/SiC epilayers are presented. These fault structures comprise SFs that fold back and forth from the basal plane (I1 Basal Plane Faults; BSFs) to the prismatic plane (Prismatic Stacking Faults; PSFs). Finally, the threading dislocation density reduction in AlN/sapphire films is modeled based on overgrowth of the dislocation outcrops by macrosteps which appear during a transition from step flow to 2D layer-by-layer growth.« less
  • No abstract prepared.
  • We present a Kirkpatrick-Baez optics (KB) system specially optimized to operate in the 6-13 keV X-ray range, where valuable characteristic lines are present. The mirrors are coated with aperiodic laterally graded (Ru/B4C)35 multilayers to define a 15% energy bandpass and to gain flux as compared to total reflection mirrors. For any X-ray energy selected the shape of each mirror can be optimized with a dynamical bending system so as to concentrate the X-ray beam into a micrometer-size spot. Once the KB mirrors are aligned at the X-ray energy corresponding to the barycenter of the XAS spectrum to be performed theymore » remain in a steady state during the micro-XAS scans to minimize beam displacements. Results regarding the performance of the wideband KB optics and of the spectro-microscopy setup are presented, including beam stability issues.« less