Efficient Numerical Modeling of the Magnetization Loss on a Helically Wound Superconducting Tape in a Ramped Magnetic Field

We investigate theoretically the dependence of magnetization loss of a helically wound superconducting tape on the round core radius R and the helical conductor pitch in a ramped magnetic field. Using the thin-sheet approximation, we identify the two-dimensional equation that describes Faraday's law of induction on a helical tape surface in the steady state. Based on the obtained basic equation, we simulate numerically the current streamlines and the power loss P per unit tape length on a helical tape. For R w₀ (where w₀ is the tape width), the simulated value of P saturates close to the loss power ~(2/π)P_flat (where Pflat is the loss power of a flat tape) for a loosely twisted tape. This is verified quantitatively by evaluating power loss analytically in the thin-filament limit of w₀/R → 0. For R w₀, upon thinning the round core, the helically wound tape behaves more like a cylindrical superconductor as verified by the formula in the cylinder limit of w₀/R → 2π, and P decreases further from the value for a loosely twisted tape, reaching ~(2/π)²P_flat.