Concentration Dependence of Frenkel-Pair-Defect Annealing in Electron-Irradiated Ta and Nb

Abstract

The present work is an investigation into the dose dependence of the annealing spectra of Ta and Nb from 15 to 285\ifmmode^\circ\else\textdegree\fi{}K after bombardment with 2.2-MeV electrons. Ta and Nb samples were irradiated to different defect concentrations, then simultaneously annealed isochronally from 14.7 up to 285\ifmmode^\circ\else\textdegree\fi{}K. In Ta, recovery peaks were observed at 23, 51, 65, 123, and 170\ifmmode^\circ\else\textdegree\fi{}K. The position of the peak near 170\ifmmode^\circ\else\textdegree\fi{}K is dose-dependent and shows the characteristics of a second-order reaction. In Nb, recovery peaks were observed at 26.5, 58, 95, and 135\ifmmode^\circ\else\textdegree\fi{}K. The peak at 95\ifmmode^\circ\else\textdegree\fi{}K is dose-dependent and follows second-order kinetics initially, with an apparent shift to higher order toward the end of the stage. A two-interstitial model seems to give the best fit to the data.