Evaluation of the Physical Qualities and Electrical Performances of HTS Mock-Up Magnets Wound With Various REBCO Tapes Under External Fields at 4.2 K

REBCO double pancake (DP) coils were fabricated using HTS tapes from four manufacturers: 1) THEVA (TV), 2) Shanghai Superconductor Technology (SST), 3) Faraday Factory Japan (FFJ) and 4) Fujikura (FJK). The three first tapes represent improved versions addressing issues highlighted in our prior study. During coil winding, the physical properties of each tape-specifically delamination strength and windability-were evaluated. To assess practical electrical performances and mechanical robustness, three mock-up magnets were assembled using pairs of metal-as-insulation (MI) DP coils: TV, SST, and FJK. A mock-up magnet could not be fabricated with FFJ tape due to severe coil deformation. All magnets were pre-tested in liquid nitrogen at 77 K under self-field conditions to measure coil and time constants, and joint resistances. Quench currents were evaluated under various external magnetic fields and temperatures. Additionally, the time constant before and after quench events were measured to investigate changes in contact and surface resistance.