Low-cost Manufacturing of Round REBCO Wires for Accelerator Magnets

Round REBCO wires with excellent tolerance to bend strain have been demonstrated. A 1.3 mm diameter round REBCO wire reached an engineering current density of 586 A/mm2 at 4.2 K in a background field of 20 T at a bend radius of 15 mm. This performance meets a key design requirement of Canted Cos θ CCT coils being developed for future accelerator magnets. The main roadblock to the utilization of round REBCO wire in accelerator magnets is its cost. The primary objective of this project is to reduce the cost of round REBCO wires by fivefold while maintaining the same critical current Ic at 4.2 K, 20 T. The fivefold cost reduction is being achieved by: 3fold reduction using onethird the number of higher Ic REBCO tapes which reduces both raw material and fabrication costs, 1.4x reduction by increasing manufacturing throughput and 1.2x reduction by increasing manufacturing yield. In our Phase I project, we have successfully met all these goals. Using an advanced metal organic chemical vapor deposition MOCVD process, we have fabricated 10meterlong tapes with Ic over 3000 A/12 mm at 4.2 K, 20 T which is 3x Ic of commercial REBCO tapes. We have increased the throughput of our manufacturing process by multiple improvements: 30x increase in tape slitting goal was 3x, 4x increase in the silver sputter deposition goal was 3x, and 4x increase in copper stabilizer electroplating goal was 3x, and a ~3x increase in thin substrate fabrication using a new process this was a stretch goal for 2x. The better laser slitting technology also results in a better quality of tape edges which improves the manufacturing yield. In Phase 2, we will scale up all these enhanced technologies to produce 30+ m long round REBCO wires at 5x lower cost. The Advanced MOCVD process, and highthroughput substrate fabrication, slitting, silver and copper deposition methods will all be scaled up to produce 50+ m long, symmetric REBCO tapes with 3x the Ic of commercial tapes. These tapes will used to fabricate 30+ m long round REBCO wires. Samples of lowcost wires will be provided to our national laboratory collaborators for coil winding and testing. In addition to meeting the needs of High Energy Accelerators that would operate at 20 T and beyond for High Energy Physics, the new technology would be highly impactful in the commercial market for accelerators which includes proton beam therapy in medicine, ion implantation for digital electronics, for safer use of nuclear energy, treatment of water and flue gases, pharmaceutical drug development and nuclear forensics and cargo screening for security. Additionally, our round REBCO wires can enable commercialization of HTS in power applications such as generators, motors, and transformers.