Design, fabrication, and test of a 12 T REBCO insert for a 27 T all-superconducting magnet

The higher magnetic field is an everlasting goal for researchers in the field of high-field superconducting magnets, for its vital significance to modern science and technology. After achieving our goal of 25 T superconducting magnet project, we set a more ambitious goal to obtain a central field of 27 T, by upgrading the previous 10 T REBCO (REBa2Cu3Ox, RE = rare earth) insert to 12 T. On the basis of the previous 10 T REBCO insert, the newly designed 12 T REBCO insert has an outer REBCO coil, which has the inner and outer diameters of 125 and 150 mm, respectively, and a height of 85 mm. The current grading method and the detailed stress analysis were employed in the design of the added REBCO coil. Stress analysis showed that the maximum hoop stress was reduced from 470 to 438 MPa after employing winding tension, overbanding, and cooldown. The designed highest engineering current density in this added REBCO coil is 383 A/mm2, much higher compared with the previous REBCO insert, the highest of which is only around 300 A/mm2. The rough operation margin for the previous REBCO coil and the added REBCO coil is 42.6% and 43.7%, respectively. This article mainly introduces the design, fabrication, and test results of the 27 T all-superconducting magnet in detail.