Scanning laser imaging of dissipation in YBa$_{2}$Cu$_{3}$O$_{7-δ}$ coated conductors

We investigate dc-current flow in high-$j$$_{c}$ YBa$_{2}$Cu$_{3}$O$_{7-δ}$-coated conductors by low-temperature laser scanning microscopy (LTLSM) and correlate the LTLSM response to magneto-optical imaging (MOI) and grain boundary (GB) misorientation. Because the voltage response measured by LTLSM is associated with the local electric field, while MOI shows the local magnetic field, the combination of these two techniques unambiguously shows that the dominant sources of dissipation and easy flux flow occur at and near GBs. By correlating LTLSM images to grain misorientation maps determined by electron backscatter diffraction (EBSD), we can directly observe the overloading of current paths through low-angle GBs neighboring higher-angle GBs.