REBCO coated conductor cables for accelerator magnets
The overall goal of the Phase II SBIR program was to develop high-quality CORC® cables that could be wound into long lengths required for accelerator magnets. The engineering current density (Je) should be increased from about 100 A/mm2 at 4.2 K in 20 T background field to at least 300 A/mm2. The CORC® cable performance should be verified in short samples, but also by manufacturing a small CORC® cable insert magnet and demonstrate its performance in a high background magnetic field. CORC® cables were successfully wound with a custom cable machine, in which each tape layer was wound with precise tape tension and gap spacing between tapes. A detailed optimization of winding parameters was performed for each CORC® conductor layout, based on tapes with different substrate thicknesses or tape widths. The in-field performance of CORC® cables, bent to 10 cm diameter, was successfully improved from about 100 A/mm2 at 20 T before the start of the program to 216 A/mm2 through a reduction of the tape substrate thickness from 50 um to 38 um. Further reduction to 30 um resulted in an engineering current density of 309 A/mm2. Narrow REBCO tapes with 30 um substrates allowed the introduction of thinner and more flexible CORC® wires that allowed bending to 6 cm diameter and testing in more common superconducting research magnets. Initial CORC® wire performance, when bent to 6 cm diameter, of 170 A/mm2 extrapolated to 20 T was achieved as part of this program. The performance of CORC® wires has since improved to exceed 450 A/mm2 at 20 T. The final goal of the Phase II program was to wind a small CORC® cable solenoid and demonstrate its performance in a background field of 14 T. A CORC® solenoid magnet with 10 cm inner diameter was wound from 19 meters of CORC® cable, containing a hard copper former for mechanical strength. The 4-layer, 45-turn solenoid contained stainless steel overbanding and Stycast impregnation to provide additional mechanical support to the windings. The CORC® insert magnet was successfully tested and demonstrated a critical current of 4,404 A in a 14 T background field, where the total central field was 15.86 T, and the peak field on the conductor was 16.77 T. The current in the insert coil could be safely ramped into the superconducting transition, followed by a slow ramp down of the current without inducing a quench or any heating developing in the coil. Also, no degradation in critical current was measured after about 20 high-current tests in high magnetic field, clearly demonstrating the robustness of the CORC® cable in high-field magnet applications. The CORC® insert test was the first high-current test of a high-temperature superconducting magnet in a substantial background magnetic field. The progress on CORC® conductor development for accelerator magnets during the Phase II program has resulted in several other projects that aim to develop accelerator magnets and other magnet technology using CORC® cables and wires. These include programs to develop Common Coil hybrid accelerator magnets at Brookhaven National Laboratory and canted-cosine-theta accelerator magnets at Lawrence Berkeley National Laboratory, clearly demonstrating the significant impact of the Phase II SBIR program.
- Research Organization:
- Advanced Conductor Technologies
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- SC0009545
- OSTI ID:
- 1578185
- Type / Phase:
- SBIR (Phase II)
- Report Number(s):
- DOE-ACT-09545
- Country of Publication:
- United States
- Language:
- English
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