Design and Construction of a 20-T 30-mm All HTS Conduction-Cooled User Magnet

A 20 T all REBCO conduction-cooled user magnet project is underway by Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). The REBCO magnet with no-insulation (NI) winding technique has the inner and outer winding diameters of 30 mm and 103.98 mm, respectively, and the diameter of the cold-bore is 22 mm. It consists of a stack of 10 double pancake (DP) coils wound with two different width REBCO tapes, the width of REBCO tape used for the two end double pancake is 6 mm, and the remaining DP coils is 4 mm. The operating current of the magnet is 224 A at 10 K. The inductance, maximum hoop stress and deflection angle between the conductor and z-axis are 1.57 H, 583 MPa and 1.41°, respectively. The magnetic field distortion and local stress concentration caused by screening current have been carefully considered. In addition, the electromagnetic design and parameter optimization, mechanical analysis, construction and preliminary test results of DP coils are specially discussed in this article.