Coupling loss model for multifilamentary coated conductor tapes valid in wide range of frequencies

We studied the alternating current (AC) loss in filamentized coated conductor (FCC) tapes containing a thin layer of high-temperature superconductor REBCO, subdivided in parallel strips. Filamentization reduces hysteresis losses in the superconductor when exposed to an AC magnetic field. On the other hand, the common approach of covering the tape with metallic stabilisation allows formation of current loops that couple individual filaments across metallic paths, resulting in the dissipation called AC coupling loss. Prediction of these two main AC loss components is essential in designing the superconducting devices generating AC or transient magnetic fields, such as particle accelerator magnets, the central solenoid of a fusion tokamak, or electric motors for aviation transport. In an AC loss study of FCC prepared from a patterned substrate, we observed a systematic deviation of the experimental data, particularly in the height of the loss peak, with respect to the existing models for coupling AC loss. The discrepancy was resolved by combining the consistent features of three previous models into a single formula capable of predicting the initial growth of coupling loss with frequency, its peaking, and eventually the loss reduction at further increase of frequency. Experimental verification on five samples with different tape widths and filament architectures confirmed the validity of the proposed formula.