AC Loss Characteristics of a Double Pancake Coil Wound with Multifilamentary REBCO Tape with High Inter-Filament Resistance

Reducing AC loss in superconducting AC equipment is crucial because of its substantial contribution to the cryogenic load. Decreasing the filament width can mitigate hysteresis loss of REBa ₂ Cu ₃ O _7−δ (REBCO, RE = rare earth elements) superconducting tapes, and segmenting the superconducting layer into multiple filaments is a viable reduction approach. However, filaments tend to connect when the inter-filament resistance is low. Therefore, we propose Cut and Aggregated Multifilamentary (CaAM) tapes with high inter-filament resistance achieved via the electrodeposition of polyimide across the entire tape. This tape configuration involves aligning four 1-mm-wide filaments in parallel and bonding them onto a polyimide substrate. AC loss measurements of short tapes exhibit a reduction at high magnetic fields. Additionally, we fabricated double pancake coils, each coil contained 80×2 turns, wound with monofilament tape and CaAM tape (coils A and B, respectively) and assessed the AC loss of the fabricated coils in liquid nitrogen. Experimental results indicate that the AC loss of coil B, using CaAM tape, is greater than that of coil A in the low-current region. However, they are almost identical in the high-current region. In contrast to the multifilament tapes with low inter-filament resistance, CaAM tapes indicate the possibility of loss reduction when used in coils.