Calendar of Events beta
Also available in RSS and iCalendar formats.
To report an event that is not listed, contact webmaster.
Quantitative Phase-Contrast Imaging in Bio-medical and Material Science
Speaker: Sara Mohammadi, The Abdus Salam International Centre for Theoretical Physics, Synchrotron Light Source Elettra
@ 2:00 PMView Description
Phase-contrast X-ray imaging is an invaluable tool in different applications, from material science to biological imaging. It is used for the evaluation of internal structure and the visualization of fine-scale features and defects e.g., cracks, voids and delimitations inside the sample. It is also widely used for analysis of composites and multiphase materials, where the different components have similar X-ray attenuation coefficients, e.g., in most of biological samples. For more advanced quantitative analysis, phase-contrast images need to be improved in their quality, minimizing the noise and other artificial defects arising from the acquisition and reconstruction steps. Therefore, specific algorithms are used during the reconstruction process from projections to slices. We analyzed the two most-applied phase retrieval algorithms and outlined derivations, approximations and assumptions of each one. The phase retrieval algorithms enhance significantly the contrast between different phases inside the sample and thus it improves the quality of projection images for a tomographic reconstruction algorithm. These algorithms have been applied on experimental data collected at the SYRMEP beamline of Elettra, Italy. Algorithms, based on Born-approximation and Transport-of-Intensity Equation (TIE), have been used for different kinds of test objects and biological samples (high absorbing, homogeneous, low absorbing, etc.) at various experimental conditions (sample-to-detector distances, energies, detector resolutions). Their capability and restriction in the visualization of the sample morphology, up to its tiniest details, have been evaluated. A quantitative comparison between phase-contrast and phase retrieved images has been also performed for some selected samples by using Pore3D, a software developed by SYRMEP group which is based on different functions and procedures for digital image processing of large 3D image datasets. [ Hide ]
@ 12:00 PM
Bi-2212 Wire and Cable Developments at Texas A&M University
Speaker: Kyle Damborsky, Department of Physics and Astronomy, Texas A&M University
@ 11:00 AMView Description
The high field superconductor Bi-2212 exhibits remarkable current carrying capacity in magnetic fields exceeding 20 T @ 4.2 K. While the critical current density vs. field behavior is exceptional, Bi-2212/Ag multifilament wires suffer from low critical current densities that are a fraction of the single crystal values. To date the low overall current densities, coupled with extreme processing conditions and low mechanical strength, have limited the use of Bi-2212/Ag wires in very high field magnet applications.
Transport currents in Bi-2212/Ag wires are primarily limited by the low initial packing density of the superconducting cores and are further hampered by un-optimized grain alignment. Additionally, parasitic phase formation during a complex melt processing produces inclusions which reduce the current carrying capacity. The Accelerator Research Laboratory at Texas A&M has fabricated and tested a very high core density Bi-2212/Ag monocore wire using a method that pre-textures and densifies the powder along with a simplified non-melt heat treatment processing. Details of the conductor fabrication, processing, transport, and microstructural properties of the monocore conductors will be presented. Additionally, a cable design that decreases the processing burden and increases mechanical strength of Bi-2212 conductor packages will be discussed.[ Hide ]
@ 12:00 PM
@ 2:30 PM
View past events >>