Electromagnetic coupling of twisted multi-filament superconducting tapes in a ramped magnetic field

We investigate theoretically the magnetization loss and electromagnetic coupling of twisted multi-filament superconducting (SC) tapes in a ramped magnetic field. Based on the two-dimensional reduced Faraday--Maxwell equation for a tape surface obtained with a thin-sheet approximation, we simulate numerically the power loss $P$ per unit length on twisted multi-filament tapes in the steady state. The current density profile clearly shows electromagnetic coupling between the SC filaments upon increasing the field sweep rate $\beta$. Although the $\beta$ dependence of $P/\beta$ for twisted multi-filament SC tapes closely resembles that for filaments in an alternating field, we show that the mechanism for electromagnetic coupling in a ramped field differs from that in an alternating field. We also identify the conditions under which electromagnetic coupling is suppressed for the typical sweep rate of a magnet used for magnetic resonance imaging.