Properties of Long GdBCO Coated Conductor by IBAD-PLD Method—The First GdBCO Coil Test

We have developed the first GdBa₂Cu₃O_7-x (GdBCO) coil using a 53.5 m long GdBCO coated conductor with a high end-to-end critical current (I_c) of 183 A. The coil was a 4 turns-84.5 layers (4 x 84.5) solenoid type coil with the dimensions of 28 mm in bore diameter, 30 mm in inner diameter, 70.9 mm in outer diameter, and 44.3 mm in height. The obtained central magnetic fields (B_o) were 1.19 T and 0.48 T when the operating coil currents (l_op) were 184.8 A and 74.2 A at 64 K and 77 K, respectively. The measured B_o were in good agreement with the calculated B_o. The l_op corresponded to the I_c of the conductor at the edge of the coil in the middle layer, where the magnetic field direction was around 45 degrees to the c-axis of the GdBCO layer. This is due to the fact that the GdBCO coated conductor exhibits a minimum of I_c for these magnetic field directions. Therefore, the magnetic field of the coil was determined by the intersection of the coil load line for this part to the magnetic field dependence of critical current (I_c - B) curve for the conductor in this direction. Since GdBCO coated conductor exhibits superior magnetic field dependence of critical current density (Jc - B) property to that of YBa₂Cu₃O₇_x (YBCO) coated conductor, the GdBCO coil can generate a high magnetic field compared with the coil made from the YBCO coated conductor. If the above GdBCO coated conductor in the coil is substituted by a YBCO coated conductor, the length of the conductor would be about 1.6 times longer than the present GdBCO coated conductor. For practical application, the GdBCO coated conductor is more promising than the conventional YBCO coated conductor.