Electrical properties of multilayered Nb3Sn superconducting power line conductors

Nb3Sn films and multilayer composites for possible application as superconducting power transmission line (SPTL) conductors have been fabricated using electron-beam coevaporation techniques. Both growth morphology and low field superconducting properties of the conductors have been studied and compared with SPTL requirements. The behavior of the critical current as a function of temperature and magnetic field is presented together with a study of the enhancement of flux pinning due to the inclusion of thin layers of normal metal in the superconductor. Temperature and field dependence of the 50 Hz ac loss is presented and a detailed comparison is made between the measured field-dependent dc critical current, the ac loss, the flux entry wave forms, and standard models for ac loss in the critical state. It is shown that fine-scale multilayered composite conductors can be fabricated which satisfy the ac loss and critical current requirements for SPTL operation at 10∘K on the basis of bulk properties alone without the necessity of a large surface barrier.