Novel 2G multifilamentary conductor design for AC applications

2G HTS wires need substantial development to allow ac applications with acceptable losses in ac magnetic fields perpendicular to the tape plane. Filament transposition is necessary to avoid large coupling currents and also to insure a uniform current flow through all the filaments, both of which are essential to minimize ac losses. Conductor twisting solves only the first part of the problem and is not really practical in a tape-shaped wire needing to be wound for instance into compact coils of various shapes. We set out to evaluate a new two-dimensional transposition approach for striated, multifilamentary 2G HTS wire. The new concept uses a so-called transposition zone, located along a linearly striated conductor. In this 7-10 cm long zone all filaments are transposed. The repeat distance of this transposition zone can be as short as 10 m or as long as 100 m, depending on the particular superconducting device and the anticipated ac magnetic fields. In this project a successful transposition approach with acceptable losses was developed. Both the striation method using lateral translations, and sound junction types using different materials, were demonstrated.