Field Canceling Effect in Double-Layer Roebel Tapes

The Roebel tape is a novel high-temperature superconducting (HTS) cable. By incapsulating the HTS Roebel cable into a tape, it has exclusive advantages such as high engineering current density, small critical current degradation, low AC losses, and a simple manufacturing process. This paper focuses on the field cancelling effect of the Roebel tape introduced by the specially designed patterns on the buffer layers and superconducting layers. From the results obtained by the 2D and 3D models using the T-A formulation, we find this effect can make the current distributed more uniformly and can significantly reduce the AC losses. The reason and the basic principle behind this will be revealed and analysed. To sufficiently exploit it to reduce losses, the structure parameters of the Roebel tape are optimised and an optimum solution is obtained. This paper can help better understand the Roebel tape and provide references to the future design and application of this novel HTS cable.