SBIR-STTR Award

There is substantial interest in the upgrading the existing High Energy Physics accelerators to higher energy levels so as to probe deeper into the subatomic scale and unlock the mysteries of the Universe. Such upgrades to higher energy levels would require use of High Temperature Superconductor (HTS) magnets which can generate magnetic fields levels of 20 T and beyond. Canted Cosine Theta (CCT) beam steering magnets using a smaller bend radius winding configuration is a leading design to generate multipole magnetic fields. A promising HTS candidate for use in accelerator magnets is RE-Ba-Cu-O (REBCO, RE=rare earth) coated conductors that are fabricated by a reel-to-reel thin film process. A challenge with REBCO coated conductors is their flat rather than a round geometry which makes it difficult to use them in accelerator magnets of complex shapes. Recently, we developed an innovative approach to fabricate round REBCO wires of 1.3 to 2 mm diameter using ultra-thin REBCO tapes where the superconductor film is positioned near the neutral plane. Such Symmetric Tape Round (STAR) wires exhibit excellent tolerance to bend strain with a critical current retention of more than 95% when bent to aradiusof15mmandanengineeringcurrentdensity(Je)ofnearly 600 A/mm2 at 4.2 K in a background field of 20 T. AMPeers has successfully scaled up fabrication of STAR wires to 60 meter lengths. The cost of STAR wires (or for that matter any round REBCO wire technology) is currently an impediment to large-scale commercialization. The main contributors to the cost of STAR wires are: the cost of individual REBCO tape strands used, fabrication cost and manufacturing yield. In the proposed program, AMPeers and University of Houston (UH) will tackle all three contributors to achieve a 5 fold reduction in the cost of STAR wires. 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, the round REBCO wire technology developed in this program can enable commercialization of HTS in power applications such as generators, motors and transformers.

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 ? 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.