Critical current of multifilamentary Nb3Sn conductors up to 18 t

The critical current l_c of Nb₃Sn conductors containing 1615 or 3721 filaments was measured in magnetic flux densities up to 18 T. The magnetic field was generated by a Bitter magnet. The overall current density of the conductor was $\text{5 × 10}{}^4\text{A cm}{}^{\mathrm{?2}}$ at 10 T and 5 × 10³ A cm^?2 at 18 T. Values of up to 21.6 T were obtained for the upper critical flux density B_c2. The influence of the diffusion conditions upon l_c, B_c2 and the superconducting transition temperature T_c have been related to the fraction of the total conductor cross-section taken up by Nb₃Sn. This fraction serves as a rough measure of the pressure exerted upon the Nb₃Sn within the conductor.