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 IBAD (ion-beam assisted deposition) and the PLD (pulse-laser deposition) method can be determined by the magnetic-knife method with spatial resolutions of 0.2 mm lateral and 10 mm longitudinal directions, respectively. In an up-to-date 80A-class YBCO coated conductor, the J c is relatively uniform in the central part and reaches 7$ × $10 9 A m -2 , while the J c fluctuates spatially in the central part of a tape fabricated earlier and with less critical current. Near the edges of the tapes, the J c is higher or lower than in the central part and the experimentally determined J c distributions 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 error in the estimated AC losses.