Experimental Study on No-Insulation HTS Coil With Solder-Free Lap Joint Inserted

This article presents a method for fabricating high-temperature superconducting (HTS) coils that does not require any soldering. No-insulation (NI) winding technique was used to fabricate double-pancake (DP) HTS coils with a “contact lap joint,” which is a lap joint without any soldering. The coils were cooled to 77 K in a liquid nitrogen bath and tested for performance using measurements of terminal voltage and central magnetic field. We also applied a lumped-circuit model to the coils to estimate key magnet parameters, including critical current, n-value, and joint resistance. Finally, we discussed the relationship between winding stress and joint resistivity, as well as the Joule heat dissipation caused by the contact lap joint.