Nondestructive Diagnostics of Narrow Coated Conductors for Electric Power Applications

We have succeeded in characterizing local critical currents and electromagnetically equivalent widths of slit coated conductors (CCs) as a function of their longitudinal position based on reel-to-reel scanning Hall-probe microscopy (RTR-SHPM). The aim is to make a quality control of slit CCs intended for electric power application, such as electric power cable in particular, for ac losses reduction. Long pieces of slit CCs, i.e., collectively 40-m-long pieces of 2-mm-wide slit CCs, were transferred in their longitudinal direction, and continuously magnetized in a liquid nitrogen bath; the magnetic field distributions of the samples were then measured by scanning a Hall sensor. From the magnetic field distributions, we could evaluate local critical currents and the equivalent widths of the slit CCs as a function of their longitudinal position. The difference between the equivalent width and the geometrical width of a CC corresponds to the damage due to the slitting process. This means that we can discuss such damage precisely together with its statistics along the longitudinal direction. This kind of diagnostics will be a very powerful technique for establishing slitting processes for producing narrow CCs for overcoming the issue of ac losses for electric power application comprising CCs.