Variation of of Binary and Ternary Alloyed RRP and PIT Wires Exposed to Fast Neutron Irradiation at Ambient Reactor Temperature

The variation of Tc and Jc for a series of binary and ternary alloyed Nb3Sn wires of the RRP and PIT type has been investigated after fast neutron irradiation (E>;0.1 MeV) at the TRIGA reactor in Vienna up to a fluence of φt = 1.4 × 1022 m-2. In contrast to Ti alloyed bronze route Nb3Sn wires, where a maximum is observed at around 0.4 ×1022 m-2, it was found that the maximum of (Jc/Jc0) versus φt in the present ternary alloyed wires was still not reached. A comparison with an earlier study on bronze route wires at RTNS-II shows that the variations of Tc versus φt and Jc versus φt do not scale: a substantially higher Jc value is now observed for the same Tc value. The degree of atomic ordering being comparable, the shift of the maximum of Jc/Jc0 with fluence is attributed to radiation induced “defect clusters.” Two observations are used for explaining the observed effect: (a) a shift of (Jc/Jc0)max toward higher fields, observed for binary bronze wires with higher Sn contents and (b) by calorimetry, the average of the Tc distribution in the filaments of RRP and PIT wires is found to occur at values up to 1.5 K higher than in bronze wires. The present data suggest that the effect of “defect clusters” is higher for wires with higher average Sn contents.