Long‐Length YBCO Coated Stainless Steel Tapes with High Critical Currents

Abstract

Progress in manufacturing 40m long YBCO coated stainless steel tapes by ion beam assisted deposition and by high‐rate pulsed laser deposition is reported. A critical current of 84.5A (77K, self field) was observed for end‐to‐end measurements of the 40m long tape based on a 1.05μm thick and 3.6mm wide YBCO film. This implies that a critical current of 235A per cm‐width is achieved by just a 1 μm thick YBCO layer. Analysis of the influence of local defects onto the integral U(I) curves allowed to formulate a general criterion for the homogeneity in terms of reduced number of tape parameters.A deterioration of tapes induced by mechanical torsion starts at a very high deformation degree: irreversibility threshold corresponds to 3000 angular degrees per meter for 4mm wide coated tape loaded with a 40N tensile axial force.