Heavy-Ion—Induced Defect Production at Low Temperature in SuperconductingNb3Sn and Effects of Saturation

Abstract

Critical temperature $T_c$ and transition width $T_{\varphi }$ of 5-μm ${\mathrm{Nb}}_3$Sn samples (chemical vapor deposition) have been measured as functions of 25-MeV oxygen irradiation below 30 K and isochronal annealing up to 410 K. After the known strong reduction, $T_c$ shows at high fluences leveling-off effects, a flat minimum followed by an increase revealing competing superimposed disorder mechanisms. Significant recovery of $T_c$ and $T_{\varphi }$ to lower values is observed. Results are discussed in terms of atomic disordering and compared to $n$ and He experiments at room temperatures.