Author: Wang, M.
Paper Title Page
THP020 Study of Dislocation Content Near Grain Boundaries using Electron Channeling Contrast Imaging and its Effect on Superconducting Properties of Niobium 876
  • M. Wang, T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  • S. Balachandran, S. Chetri, P.J. Lee
    NHMFL, Tallahassee, Florida, USA
  • S. Chetri, A. Polyanskii
    ASC, Tallahassee, Florida, USA
  • C. Compton, C. Compton
    FRIB, East Lansing, Michigan, USA
  • C. Compton
    NSCL, East Lansing, Michigan, USA
  Funding: U.S. Department of Energy. National Science Foundation Cooperative Agreement No. DMR-1157490 (-2017) DMR-1644779 (2018-) and the State of Florida
Trapped micro-Tesla levels of magnetic flux degrade the performance of Nb superconducting radio frequency (SRF) accelerators. Recent studies have revisited the role of small deformation (dislocation substructure influence) on cavity performance. However, the link between microstructural defects and mechanisms leading to poor performance is still unresolved. To examine the mechanism of flux pinning by dislocations and grain boundaries, systematic studies on bi-crystal Nb tensile samples were designed with strategically chosen orientation relationships between neighboring crystals with respect to the grain boundaries. Laue X-ray diffraction and electron backscatter diffraction analysis was used to measure crystal orientations of a large-grain Nb slice, from which the bi-crystals were extracted. Dislocation structures near the grain boundaries were characterized before and after 5% tensile deformation using electron channeling contrast imaging (ECCI), after which the magnetic flux behavior was observed using cryogenic magneto-optical imaging (MOI). We discuss the conditions under which we observe increased flux pinning in regions of high dislocation density.
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About • paper received ※ 23 June 2019       paper accepted ※ 30 June 2019       issue date ※ 14 August 2019  
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