Test and Analysis of Laboratory-Scale D-Shaped Co-Wound No-Insulation HTS Single Pancake Coil for TF Coil Application

No-insulation (NI) high temperature superconductor (HTS) toroidal field (TF) coil or its variations have been regarded as potential options for a compact, high magnetic field tokamak due to compactness in size and robustness in operational reliability. However, its real application still faces multiple challenges, e.g., limited experience in the design, construction, and operation of “D-shaped” NI HTS coils for toroid magnets. Here we report, as the first attempt in Korea, fabrication, test, and analysis of a reduced size D-shaped NI HTS single pancake coil to explore the feasibility of NI HTS technology in TF coil. The D-shaped NI HTS coil is designed to be 1/20 of the Korea Superconducting Tokamak Advanced Research (KSTAR) TF coil in height. One of the three test coils is wound with single HTS tape, and the other two test coils are co-wound with double and triple tapes, respectively. Current charging/discharging tests and sudden discharge tests were conducted for each coil, and the results are analyzed by the well-known lumped circuit model of a typical NI HTS coil. The results show possible variations in the contact resistance during charging and sudden discharge within a coil.