The influence of radiation damages on the superconducting properties of Nb3Sn

Samples of Nb3Sn were irradiated with various doses of protons, α-particles and fission fragments and then anneled isochronally. The changes of Isub(c)(H) and Tsub(c) as functions of the irradiation dose were investigated yielding the folowing results. 1. Tsub(c) and Tsub(c)(H) in the A15 type superconductors (compounds) are influenced considerably by crystal lattice defects. 2. The changes of Tsub(c) and Isub(c) are consequences of different types of defects. Critical current measurements show that Isub(c) is more sensitive to clusters but Tsub(c) changes are larger for the homogeneous distribution of small defects. 3. The volume pinning force changes are larger in higher magnetic fields. 4. The critical temperature decreases monotonically when the irradiation dose increases. 5. There are points of inflexion in the curves of the critical temperature versus the annealing temperature that can be related to various groups of defects having different activation energies. 6. The results indicate the possibility of a suitable treatment of A15 type superconductors to improve their current characteristics. (Auth.)