Influence of Cracks in the Superconductor Layers Caused by Mechanical Stresses on Critical Currents and AC Transport Losses in YBCO CCs

Influence of mechanical stresses on critical currents and ac transport losses in YBCO CCs with copper stabilization layers is investigated by ac loss measurement and SEM observation of surfaces of YBCO layers. Tested YBCO strips were made by slitting mechanically a wide tape. Cracks caused by the slitting were found in the YBCO layer even in the virgin strips in the edge side areas. Mechanical stresses to strips widen and grow those original cracks. In the paper, the characteristics of critical current and ac transport current losses depending on mechanical stresses are explained in relation to features of the cracks.