Introduction of the next generation of CORC^® wires with engineering current density exceeding 650 A mm^-2 at 12 T based on SuperPower's ReBCO tapes containing substrates of 25 μm thickness

Next generation particle accelerators and fusion machines will greatly benefit from the development of low-inductance magnets capable of generating magnetic fields in excess of 16 T. Such magnets require higherature superconductors capable of carrying very high currents exceeding 5 kA at current densities of 400-600 A mm^-2, such as Conductor on Round Core (CORC^®) cables and wires wound from RE-Ba₂Ca₃O_7-δ (ReBCO, Re = rare earth) coated conductor tapes. CORC^® wires containing ReBCO tapes with 30 μm thick Hastelloy^® substrates have previously been demonstrated as a viable high-field magnet conductor that can be produced at long lengths. Further improvement of the performance and flexibility of CORC^® wires would benefit from the development of ReBCO tapes with even thinner substrates. SuperPower Inc. recently demonstrated ReBCO tapes based on 25 μm thick Hastelloy^® substrates that allow the development of thinner and more flexible CORC^® wires that meet the stringent performance requirements of high-field magnets. Several tapes containing 25 μm thick substrates were produced and analyzed, exhibiting critical current and cabling performance in-line with the current production level tapes with 30-50 μm thick substrates. Tape critical current was measured at 4.2 K and applied magnetic fields up to 31.2 T. Several CORC^® wires incorporating these tapes were manufactured by Advanced Conductor Technologies using similar winding procedures that previously resulted in high-quality magnet-grade CORC^® wires based on tapes with 30 μm thick substrates. The CORC^® wires were tested in an applied magnetic field up to 12 T after bending to a 63 mm diameter. A critical current as high as 6231 A (12 T, 4.2 K) was measured with an engineering current density (J_e ) of 678 A mm^-2, which extrapolates to over 450 A mm^-2 at 20 T and is the highest current density reported in a CORC^® conductor to date. The combination of ReBCO tapes produced using 25 μm thick substrates and the ability to wind them into long-length, high-quality CORC^® magnet wires brings the development of low-inductance accelerator and fusion magnets that operate at magnetic fields exceeding 20 T closer to fruition.