Stage I Recovery Spectrum of Pure Copper Irradiated with Electrons over the Range 1.25 to 3.25 MeV

A 99.999% pure copper specimen was irradiated at 20.4^∘{}K with 1.25-, 1.48-, 2.15-, 2.25-, and 3.25-MeV electrons. After irradiation at each energy the specimen was isochronally annealed to 60^∘{}K. Electrical resistivity at 20.4^∘{}K was the parameter measured. The results show that Stage I recovery is more complex than previously expected. The data show eight definite recovery substages and strongly indicates that possibly nine recovery substages exist in Stage I recovery. All substages were relabeled I₁ through I₉ for convenience. The new substages confirmed were labeled I₂, I₇, and I₉. Substage I₂ occurs at 22-23^∘{}K and represents 1.5-2% recovery. Substage I₇ occurs at 45^∘{}K, is dose-dependent, and appears more clearly resolved after the higher energy irradiations. This substage, I₇, may correspond to the "bump" found at about 50^∘{}K by Nilan and Granato. I₉ occurs at 53-59^∘{}K, represent 1% recovery and appears to be dose-dependent. I₉ occurs near the temperature of the IIₐ substage reported by Sosin and Neely for doped copper. The shape of the isochronal derivative on the high-temperature side of I₅ (ID former notation) indicates that another substage, I₆, may be present. A similarity was noted between the recovery spectrum of gold and the new recovery spectrum of copper. A comparison with the results of others concerning the percent recovery associated with IB and IC (former notation) as a function of bombarding electron energy, supports the conclusion that not much change in population of IB or IC occurs beyond $E=1.2$ MeV.