Controllability of the Contact Resistance of 2G HTS Coil With Metal Insulation

The turn-to-turn contact resistance of second-gene-ration (2G) HTS coil with metal insulation is a very important parameter in the viewpoint of the stability and current charging speed of the HTS coil. Controllability of the contact surface resistance of the 2G HTS coil with advanced metal insulation was observed in contrast with the case of the stainless steel (SS) metal insulation (MI). Three types of model coils-a no insulation coil, a metal insulation coil cowound with SS tape, and an MI coil cowound with copper (Cu) electroplated SS tape-were prepared and evaluated. The contact surface resistances between two Cu-plated 2G HTS tapes, between a Cu-plated 2G HTS tape and an SS tape, and between a Cu-plated 2G HTS tape and a Cu-plated SS tape are 6.3, 362.4, and 7.9 μ Ω·cm
²
, respectively. Dramatic reduction of the turn-to-turn contact surface resistance in model coils was achieved by using MI coil cowound with the Cu-plated SS tape. Also, the possibility of changing such contact surface resistance will be useful for designing the MI magnet.