Demonstration of current sharing around tape defects in a low-inductance CORC® wire solenoid generating a peak magnetic field of 4.6 T at 25 K

This manuscript presents the design, fabrication, and operation of high temperature superconducting conductor on round core (CORC ® ) wires utilizing variable critical current REBCO tapes that contain occasional dropouts of critical current ( I c ). Performance evaluations conducted at temperatures ranging from 25 K to 77 K demonstrated comparable superconducting characteristics between CORC ® wires with and without intrinsic variations in I c within the REBCO tapes. This is a clear indication that the high level of current sharing between tapes in CORC ® wires allows current to bypass local defects. A 70 mm bore, 4-layer CORC ® solenoid in which 25 m of CORC ® wire was wound into 81.5 turns, generated a peak magnetic field of 4.6 T at an I c of 4460 A at 25 K. The I c of the solenoid corresponds closely with the sum of the expected average tape I c , not its minimum I c driven by the tape dropouts. Experimental results confirmed stable dissipative operation at 4021 A (87% I c ) continuous current with minimal power losses, highlighting the feasibility of manufacturing longer-length CORC ® conductors from tapes with significant local dropouts for superconductor applications including fusion, accelerators, power transmission, and rotating machinery.