Analytical and experimental investigation of electrical characteristics of a metallic insulation GdBCO coil

This paper presents results, experimental and analytical, of the electrical characteristics of GdBCO single-pancake coils co-wound with a brass tape as metallic insulation (MI coil). The GdBCO pancakes were subjected to sudden discharge, charge-discharge, and over-current tests. The sudden discharge and charge-discharge test results of the MI coil demonstrated that MI coils can be charged and discharged significantly faster than non-insulated coils that are wound only with GdBCO tape. In over-current tests at 150 A (1.25I_c), the MI coil exhibited better electrical behavior, i.e., self-protecting features, than its counterpart co-wound with Kapton tape, an insulator. Moreover, the experimental and analytical results are in agreement, validating the use of a concise equivalent parallel-RL circuit model for the MI coil to characterize its electrical behavior. Overall, the MI winding technique is highly promising to help build compact, mechanically robust, and self-protecting magnets composed of REBCO pancake coils. With no organic material in the winding, MI REBCO pancakes will be immune to neutron radiation damage, making the MI winding technique a viable option for fusion reactors, such as for toroidal field, poroidal field magnets, and central solenoid.