Effect of irradiation with 32-MeV protons on critical parameters of modern Nb$_3$Sn-based superconducting composite wires

Vibrating-sample magnetometry techniques has been used for investigation of the electrophysical characteristics of several types of modern commercial multistrand composite wires based on Nb3Sn superconducting compound at temperatures that were measured 4.2, 7, and 12 K in magnetic fields up to 8 T before and after irradiation of the samples by fast (32-MeV) protons to fluences values $\phi t$ = 3 $\times$ 10$^{16}$, 1 $\times$ 10$^{17}$, 3 $\times$ 10$^{17}$, and 1 $\times$ 10$^{18}$ cm$^{-2}$. All samples irradiated to fluences values up to $\phi t$ = 1 $\times$ 10$^{17}$ cm$^{-2}$ exhibited growth of the critical current density, which was most sharply pronounced in strong magnetic fields at lower temperatures. Further irradiation to a fluence value of $\phi t$ = 1 $\times$ 10$^{18}$ cm$^{-2}$ led to decrease of the critical current density below the initial level. The critical temperature of samples monotonically decreased with increasing irradiation dose.