Changes in superconducting properties by room temperature neutron irradiation for binary and alloyed Nb 3 Sn multifilamentary wires

The critical parameters T c , J c and B* c2 of binary and Ta, Ti, Ni+Zn alloyed multifilamentary Nb 3 Sn wires have been determined after room temperature irradiation at the 14 MeV neutron source in Livermore. J c measurements were made in transverse magnetic fields up to 20 T. In all the investigated cases, neutron irradiation caused an initial enhancement of J c , followed by a decrease at higher doses. In the alloyed wires the enhancement in J c occurs at much Lower doses with respect to binary wires (between 1.5 and 3 × 10 17 n/cm 2 depending on the alloying element. In the high fluence region (above 10 18 n/cm 2 ) for alloyed wires J c is considerably reduced below the initial J co value measured in unirradiated samples, while for binary wires the J co values at 3 × 10 18 n/cm 2 are still higher than J co . In binary wires, B* c2 is increased by about 10% at J cmax , in contrast to alloyed wires, where this initial increase is considerably reduced. Changes in the electrical resistivity σ o are used to explain the trends observed in the different samples.