Materials for classical and high-Tc superconducting tapes and wires at 4.2 K

For the next few years, the classical materials NbTi and Nb3Sn will still remain at the centre of interest for the construction of magnets operating at temperatures between 1.8 and 4.2 K. Magnets operating in the persistent mode at fields >20 T and laboratory magnets approaching 23 T can be envisaged in the near future, based on Nb3Sn and Nb3Al wires. The actual situation of critical current densities as a function of the applied field at 4.2 K is briefly reviewed. Considerably higher fields will be produced using insert magnets based on Bi(2212) and Bi(2223) tapes, provided the mechanical properties can be improved.