Mössbauer effect studies on 2-MeV proton irradiatedNb3Sn

Abstract

Temperature-dependent recoil-free fraction M\ossbauer studies on virigin, 1.65-MeV $^{1}\mathrm{H}$- and 2.0-MeV $^{1}\mathrm{H}$- irradiated, and 185-Mrad $\ensuremath{\gamma}$-irradiated ${\mathrm{Nb}}_{3}$Sn have been carried out in the range $78\ensuremath{\le}T\ensuremath{\le}320$ K, using the 23.8-keV radiation of $^{119}\mathrm{Sn}$. These data permit the calculation of an effective lattice temperature, ${\ensuremath{\Theta}}_{M}$, as probed by the motion of the tin atom. The data indicate that a proton dose rate of \ensuremath{\sim}1.2 \ifmmode\times\else\texttimes\fi{} ${10}^{19}$ charges ${\mathrm{cm}}^{\ensuremath{-}2}$ lowers ${\ensuremath{\Theta}}_{M}$ by \ensuremath{\sim}50\ifmmode^\circ\else\textdegree\fi{} owing to the creation of a statistical distribution of site defects which increase the low-frequency density of states of the phonon spectru. These site defects can be annealed out at \ensuremath{\sim}750\ifmmode^\circ\else\textdegree\fi{}C. ${\mathrm{Nb}}_{3}$Sn is exceptionally stable to $\ensuremath{\gamma}$ radiation damage effects, a dose of 185 Mrad incident on a foil sample apparently has no effect on ${\ensuremath{\Theta}}_{M}$ as probed by the tin atom.