Coupling losses in filamentary superconductors with a resistive barrier

An equivalent circuit model is used to calculate the coupling losses in a filamentary superconductor with a resistive barrier round the filaments. The results depend on the parameter N root(R/r) where N is the number of filaments along the field direction, R is the usual transverse resistance, and r is the resistance across the barrier. When this parameter is small current is transferred to filaments throughout the cross section and the loss is mainly due to currents crossing the barrier. In this limit the loss is multiplied by a factor (NR)-R-2/3r, which is much smaller than unity for large r. Since current is not transferred from the matrix by only the surface layer of filaments, saturation effects are reduced. To take advantage of this reduction in loss not only the barrier resistance has to be greater than the transverse resistance, but also the number of filaments along a field line has to be as small as possible. The criterion is that (NR)-R-2/r should be less than one.