Hybrid accelerator magnets based on dog bone shaped CORC® wire inserts for operation beyond 20 T
- Advanced Conductor Technologies LLC, Boulder, CO (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
High field magnets capable of generating magnetic fields exceeding 20 T are needed for next generation particle accelerators such as a High Energy LHC or a Future Circular Collider. NbTi and/or Nb3Sn dipole outserts are being developed to provide the initial 12 – 15 T background field within a 120-130 mm bore [1]–[3]. A compact insert made from high-temperature superconductors (HTS) is therefore needed to generate the final 5 – 8 T within a final aperture size of 40-50 mm diameter. Such an insert needs to be operated at high engineering current density (Je) at currents of 5 – 20 kA. This program aims to develop HTS accelerator insert magnets, in which the relatively large minimum conductor bending radius results in a conductor-friendly design, that can be combined with a low-temperature superconducting (LTS) outsert to form a 20 T hybrid dipole magnet using current-state-of-the-art CORC® wires. One of the challenges of producing a compact HTS insert magnet with a 40-50 mm diameter aperture is the bending constraints placed on the conductor because traditional saddle and racetrack coils around such an aperture would require bending radii of less than 20 mm. CORC® wires are the most flexible high-current HTS solution that can be bent in any direction, but the present generation of CORC® wires have a minimum bend radius of about 30 mm before significant degradation to their performance occurs [4]. Advanced Conductor Technologies (ACT) has teamed up with Lawrence Berkeley National Laboratory (LBNL) to develop dog bone shaped insert dipole magnets wound from current state-of-the-art CORC® wires. The dog bone shape allows for the design of compact dipoles to achieve a high transfer function while preventing bending of the conductor below 35 mm radius, which ensures a high Ic performance. In Phase I we demonstrated the feasibility of winding high-performance HTS magnets using CORC® wires with conductor friendly bends at the poles. Conductor performance after bending and within a 12 T background field was verified, confirming the bending limitations of present-day CORC® wires and demonstrating the potential to achieve higher levels of performance by designing magnet coils that consider these bending constraints. Several coil designs using dog bone shapes were conceived and tested using subscale structures with a limited number of turns. A small 2-turn coil was wound using CORC® wire that had similar performance before and after being wound, where tape Ic performance was only decreased by 6 % at the 40 mm minimum bend in the coil’s end. One of the most promising layouts developed, where the coils are wound like AC motor windings with distributed windings, herein called the Winding-In-Stator-like Configuration (WISC) magnet concept, shows a lot of potential. Initial modeling confirmed that the concept can be used to create compact HTS dipole magnets with a large radius of curvature at the poles where the peak field on the conductor is also limited. The Phase I outcome makes a strong case for continuation into a Phase II program where additional optimization, stress analysis, and the design and manufacturing of more substantial model coils will be the next steps to fully develop the technology needed to make 20 T dipole magnets a reality.
- Research Organization:
- Advanced Conductor Technologies
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- SC0021687
- OSTI ID:
- 1969409
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-ACT-21687
- Country of Publication:
- United States
- Language:
- English
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