Experimental determination of two-dimensional critical current density distribution in YBCO coated conductors

The critical current density (J(c)) distribution in YBCO coated conductors is attracting interest from the viewpoint of its influence on their AC loss characteristics as well as from material science and process engineering. A two-dimensional J(c) distribution in a YBCO coated conductor made by the MAD (ion-beam assisted deposition) and the PLD (pulse-laser deposition) met hod can be determined by the magnetic-knife method with spatial resolutions of 0.2 mm lateral and 10 mm longitudinal directions, respectively. In an u p-to-date 80A-class YBCO coated conductor, the J(c) is relatively uniform i n the central part and reaches 7 x 10(9) A m(-2), while the J(c) fluctuates spatially in the central part of a tape fabricated earlier and with less c ritical current. Near the edges of the tapes, the J(c) is higher or lower t han in the central part and the experimentally determined J(c) distribution s are far from uniform. This suggests that a presumption of a uniform J(c) for AC loss estimations is not always reasonable and can lead to a large er ror in the estimated AC losses.