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