Multi-filament HTS cables to reduce AC loss: proof-of-concept experiments and simulation

Reducing ac losses of high-temperature superconducting (HTS) is essential for ac application since it can lower the constraint on the cryogenic cooling demand. Several studies have reported that the manufacturing of multifilament HTS cables can reduce ac loss. However, large coupling losses were identified in the existing cables, due to the existence of coupled copper or soldering layers. We report in this article a novel way to develop multifilament HTS cables, mainly focusing on suppressing the coupling losses by reducing the contact resistivity within the HTS cables. Heat shrink tubes are used to directly insulate narrow HTS filaments into a cable structure. Sample cables were made with 4 mm and 2 mm wide HTS strips. Both transport losses and total ac losses in a rotational magnetic field were measured to quantify the ac loss reduction for the multifilament HTS cables. The measurements were used to validate the modeling results, and to predict ac loss reduction for 1 mm wide HTS cable. The results showed loss reduction up to around 90% in the 1 mm wide HTS cable compared with 4 mm cable. As a result, the proposed multifilament HTS cables will have promising applications in reducing ac loss.