Development of YBCO insert for a 25 T all superconducting magnet

Recently, a superconducting magnet with the center field of 25 T at 4.2 K and a warm bore-size of 32 mm in diameter has been designed and fabricated in Institute of Electrical Engineering (IEE). The 25 T superconducting magnet consists of NbTi, Nb3Sn and YBCO inserts. YBCO insert has been designed, fabricated and tested in the liquid helium at IEE so as to prove the technical feasibility to achieve the target of 25 T. The critical current distribution, hoop stress, radial stress and fabrication techniques are addressed. The YBCO insert has the inner diameter, outer diameter, and height of 24 mm, 65 mm, and 204 mm, respectively. The YBCO insert was assembled with a Bi2223 magnet which provide a background magnetic field of 5.8 T with a design operating current of 150 A. As for the YBCO insert, a 5.3 T central magnetic field can be obtained at the design operating current of 150 A. Test results show that a 5.5 T central magnetic field can be obtained in the central bore of YBCO insert at the operating current of 150 A, self-field; and the combination of these two insert coils can generate a center magnetic field of 11 T at 4.2 K. In this paper, the design, fabrication and preliminary experiment are reported.