Variation of (Jc/J_ c0)ₘₐₓ of Binary and Ternary Alloyed RRP and PIT Nb₃Sn Wires Exposed to Fast Neutron Irradiation at Ambient Reactor Temperature

The variation ofTcandJcfor 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 × 1022m-2. In contrast to Ti alloyed bronze route Nb3Sn wires, where a maximum is observed at around 0.4 ×1022m-2, it was found that the maximum of (Jc/Jc0) versus φtin 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 ofTcversus φtandJcversus φtdo not scale: a substantially higherJcvalue is now observed for the sameTcvalue. The degree of atomic ordering being comparable, the shift of the maximum ofJc/Jc0with fluence is attributed to radiation induced “defect clusters.” Two observations are used for explaining the observed effect: (a) a shift of (Jc/Jc0)maxtoward higher fields, observed for binary bronze wires with higher Sn contents and (b) by calorimetry, the average of theTcdistribution 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.