Flux shear and critical current density of superconducting Nb₃Sn

For superconducting Nb3Sn the critical current, or pinning force, density as a function of grain size and applied magnetic field data are shown to be in general agreement with computations based on flux-line-lattice shear, activated by Frank-Read source dislocations. The formalism predicts an optimum effective grain size and maximum critical current density which can be sustained at a given applied magnetic field. Neutron irradiation effects are also consistent with predicted results