Saturday, 3F-05, 9:10-9:20

Spatially Resolved Study of Dissipation at Different Magnetic Fields in RABiTS Coated Conductors

Dmytro Abraimov

Pei Li, David Larbalestier

Applied Superconductivity Center, National High Magnetic Field Laboratory, 242 Shaw Building
2031 East Paul Dirac Drive, Tallahassee, FL 32310

Xiaoping Li, Marty Rupich

American Superconductor Corporation, 64 Jackson Road, Devens MA 01434 USA

To understand the influence of current limiting mechanisms (CLM) in YB₂Cu₃O_7-d coated conductor (CC) at different magnetic fields (B) we employ Low Temperature Scanning Laser Microscopy (LTLSM) to reveal the local electric field (E) distributions. This is combined with orientation imaging microscopy to reveal the grain boundary (GB) structure. Results with several different types of links will be discussed. For polycrystalline links, as the magnetic field is increased we observe a smooth transition from a GB to a bulk limited regime. At small B, the dissipation is strongly inhomogeneous and generally follows the GB network with enhanced values along low angle GBs and at the edges of bottlenecks defined by higher misoriented GBs. We observed that inhomogeneous flux jets can lose their structure at magnetic fields below 1 T. In links with an abundance of highly-misoriented grains (HMG) the HMGs are current limiting mechanisms up to 5T. For links with low concentrations of HMG, the dissipation pattern at 5 T is defined by the link geometry rather than the GBs, which means the risk of developing hot spots at GBs is considerably decreased. For narrow, one-dimensional CC links, the I_c distributions were calculated for different magnetic fields. In wider, two-dimensional links where we applied B //ab, the electric field is more homogeneous and appears as straight lines that follow the external magnetic field. In the nominal "Lorentz force free regime" where the field is nominally parallel to the current, the dissipation is highly sensitive to defects.

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