Feasibility Study for Elimination of the Screening Current-Induced Fields in HTS Coil

Abstract

Herein, we report a feasibility study for elimination of the screening current-induced field (SCIF) in fully insulated (INS) and no-insulation (NI) GdBCO coated conductor (CC) coils exposed to an external AC magnetic field generated by background solenoid copper coils. Prior to investigating the effects of external AC magnetic fields on SCIF in the GdBCO CC coils, the magnetic flux density (B z ) was calculated using the equivalent circuit model and compared to the B z obtained empirically to quantify the SCIF in the INS and NI coils. The value of the SCIF in the NI coil was smaller than that in the INS coil without the use of an external AC magnetic field, due to the current paths originating from the turn-to-turn and layer-to-layer contacts, suggesting that the screening current dissipated by contact resistance during charging. When the INS and NI coils were exposed to the external AC magnetic field, the B z of the coils increased gradually, and eventually saturating to the calculated B z values, indicating full removal of the SCIF. In addition, the SCIF of the NI coil could be removed under subjection to a lower external AC magnetic field compared to the INS coil, due to the lower SCIF occurring in the NI coil after charging.

Vortex shaking study with use of linear voltage–current law

“…It consists in applying a small AC magnetic field orthogonally to the tape magnetization to accelerate its relaxation. Several experiments have demonstrated the efficiency of this approach [2][3][4].…”