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

Abstract

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 Bi/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ 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 /spl sim/20%. The magnet has been operated in liquid cryogens and has achieved engineering current densities of 900 A cm/sup -2/ at 77 K and 6680 A cm/sup -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/sup -2/ was achieved at 12 K.