Changes in superconducting properties by room temperature neutron irradiation for binary and alloyed Nb3Sn multifilamentary wires

The critical parameters Tc, Jcand B*c2of binary and Ta, Ti, Ni+Zn alloyed multifilamentary Nb3Sn wires have been determined after room temperature irradiation at the 14 MeV neutron source in Livermore. Jcmeasurements were made in transverse magnetic fields up to 20 T. In all the investigated cases, neutron irradiation caused an initial enhancement of Jc, followed by a decrease at higher doses. In the alloyed wires the enhancement in Jcoccurs at much Lower doses with respect to binary wires (between 1.5 and 3 × 10¹⁷n/cm²depending on the alloying element. In the high fluence region (above 10¹⁸n/cm²) for alloyed wires Jcis considerably reduced below the initial Jcovalue measured in unirradiated samples, while for binary wires the Jcovalues at 3 × 10¹⁸n/cm²are still higher than Jco. In binary wires, B*c2is increased by about 10% at Jcmax, in contrast to alloyed wires, where this initial increase is considerably reduced. Changes in the electrical resistivity σoare used to explain the trends observed in the different samples.