Transport AC losses in round superconducting wire consisting of two concentric shells with different critical current density

The AC transport losses in a round wire consisting of two concentric shells with different critical current densities have been calculated. The simplicity of the used model allowed the solution to be found analytically, It is found that if the outer shell has poorer properties (i.e. lower J(c)) with respect to the core, then the transport AC loss will be higher than expected for a homogeneous wire with the same I-c. However, lower losses compared to a homogeneous wire are expected if the outer part has superior properties than the inner one, In either case, the loss curve for the non-homogeneous wire exhibits a different shape to that of a homogeneous wire. Such a different 'shape' in the loss curve, in addition to a loss level notably different from that predicted by the homogeneous model, on the basis of experimentally determined critical current, is a strong indication of the wire inhomogeneity. (C) 1997 Elsevier Science B.V.