A detailed study of the design, construction and cryo-operation of an HTS magnet

The design, construction, and characterization of a high temperature superconducting (HTS) magnet is described. The design stage has involved the development of computer software for the calculation of the critical current of a solenoid wound from anisotropic HTS conductor. This calculation can be performed for a variety of problems including those involving magnetic materials such as iron by the incorporation of finite element electromagnetic analysis software. This has enabled the optimization of the magnet´s performance. The HTS magnet is wound from 190 m of silver-matrix Bi₂Sr₂Ca₂Cu₃O₁₀ powder-in-tube tape conductor. The dimensions are 70 mm bore and 70 mm length, and it consists of 728 turns. Iron end-plates were utilized in order to reduce the radial magnetic field, and consequently increase the performance by ∼20%. The magnet has been operated in liquid cryogens and has achieved engineering current densities of 900 A cm^-2 at 77 K and 6680 A cm^-2 at 4.2.K. The HTS magnet has been operated by conduction-cooling on a mechanical refrigerator at various temperatures in the range 12 to 50 K. The thermal stability in this relatively low cooling-power system has been assessed. An engineering current density of 5600 A cm^-2 was achieved at 12 K.