Recent Development of the 25 T All-Superconducting Magnet at IEE

Institute of Electrical Engineering, Chinese Academy of Sciences has been focusing on high-field all-superconducting magnet project for many years. No-insulation (NI) winding technology, despite of its charging delay time, makes the magnet of much higher current density, and more important, self-protected. Based on the NI dry-winding technology, a 25 T/32 mm bore superconducting magnet was designed as a combination of 15 T/160 mm bore low temperature superconductor magnet and a 10 T/32 mm bore high temperature superconductor insert. A prototype coil, composed of 15 double pancakes (DPs), was tested at 4.2 K. Test results show that the REBCO insert can generate a 9 T central field in a 15 T background field, and 11.2 T, self-field. While fully evaluation of this insert shows that bad splice joints and premature quenches occurred during the test. We have repaired the bad splice joint, replaced some broken DPs, and rebuilt some double-wound DPs to lower the current density at the top/bottom of the insert to improve the operation margin. After that, we will retest the magnet system. The latest design, construction, and test results of the 25 T all-superconducting magnet will be fully introduced in this paper.