Hysteresis and Coupling Loss in Filamentized REBCO Tapes

Use of coated conductor tapes from high-temperature superconductors is a possible way for better energy efficiency in large magnetic systems for particle accelerators or fusion tokamaks. Because the hysteresis loss in a time varying magnetic field is proportional to the tape width, a substantial gain is expected by splitting of the REBCO layer into parallel filaments. Usually, a metal layer is added to facilitate stable operation, albeit this conductive connection between filaments introduces a new kind of loss, known as coupling loss. When analyzing the experimental data of samples produced by the scalable technology, where the buffer and the superconductor layer are deposited via standard industrial procedures on a 3D patterned Hastelloy substrate, we have found that the existing models for coupling loss do not provide satisfactory quantitative predictions. This motivated us to develop an improved model for low- and mid-frequency behavior. While preserving the well-known qualitative properties foreseen by previous models, our new model enables quantitative predictions at frequencies up to 1000 Hz, without the need for adjusting the results by fitting the geometric parameters.