X-Ray Study of Deuteron-Irradiated Copper near 10°K

Abstract

Precise measurements of lattice expansion of high-purity copper held near 10\ifmmode^\circ\else\textdegree\fi{}K during deuteron bombardment were made using a rotating single-crystal method. An expansion of (4.1\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}21}$ per 7-Mev deuteron/${\mathrm{cm}}^{2}$ was found. No broadening of the Laue-Bragg intensity around the (4,0,0) reciprocal lattice point occurred. These effects are broadly consistent with the introduction of small point centers of dilatation. On the assumption that the damage consists of Frenkel defects, published calculations for the volume expansion due to interstitial atoms and vacant lattice sites in copper and the observed expansion lead to a concentration of defects which is only 0.08 to 0.22 of that predicted by the simple theory of displacement. Several independent measurements of inhomogeneity of the damage indicated an ${E}^{\ensuremath{-}1}$ variation of the probability of lattice-atom displacement with deuteron energy, $E$, in agreement with the simple theory. The ratio of resistivity increase (as determined by Cooper et al.) to lattice expansion is 7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ \ensuremath{\mu}ohm-cm for such deuteron irradiation. Use of the empirical defect concentrations then gives a value for the resistivity of 1% of Frenkel defects as 2.1 to 5.6 \ensuremath{\mu}ohm-cm.Thermal recovery of the expansion in the temperature range 10-302\ifmmode^\circ\else\textdegree\fi{}K was measured. It was strikingly similar to the recovery of electrical resistivity changes produced by deuteron irradiation. About 55% of the recovery occurred in a range below 42\ifmmode^\circ\else\textdegree\fi{}K and the recovery was essentially complete at 302\ifmmode^\circ\else\textdegree\fi{}K. Whatever the activating mechanism may be in each stage of recovery, the observed recovery appears predominantly due to mutual annihilation of interstitials and vacancies.