Fusion neutron irradiation effects in commercial Nb3Sn superconductors

This is a preliminary report on a series of fusion neutron (14.8 MeV) irradiation studies on pure and alloyed multifilamentary Nb3Sn superconductors at the Livermore Rotating Target Neutron Source RTNS-II. One set of specimens (2 pure Nb3Sn and one alloyed - (Nb-1,2 wt% Ti)3Sn - conductor) was irradiated in-situ at 14 K in 3 cycles up to a maximum fluence of 1.3x1022 n/m2 (0.32 eV deposited damage energy) and Tc and jc measured in magnetic fields up to 15.5 T. The critical parameters were also recorded after isochronal annealing cycles at 80, 180 and 300 K. Six identical sets including 3 additional wires (one pure liquid diffusion processed and 2 alloyed - (Nb-0.8 wt% Ti)3Sn and (Nb-2.0 wt% Ti)3Sn - conductors) were irradiated at room temperature at different positions from the source in order to accumulate approximately 2x, 1x, 1/2, 1/4, 1/8 and 1/16 of the maximum dose of the in-situ experiment. A comparison of the in-situ results with the room temperature irradiation data showed no significant differences in the behavior of Tc and jc as a function of neutron fluence and only small recovery effects were found after the isochronal anneals at the end of the in-situ experiment. (orig.)