High-field, high-current superconductors

Superconducting materials which have zero electrical resistance while carrying high electric current densities (around 1,000,000 A/sq cm) in high magnetic fields (up to 50 T) which may be used in the windings of loss-free electromagnets to generate high magnetic fields, are reviewed. The principles of superconductivity and high-current type II superconductors are discussed. Materials which satisfy the primary high-field superconducting magnet conductor requirements of high critical temperature and upper critical field, susceptibility to the introduction of a large number of defects, and ability to be produced by means of fine filamentary construction are examined. Finally, future possibilities for expanding superconducting magnet fields above 18 T and the developments required for this purpose are indicated.