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 ${\mathrm{I}}_1$ through ${\mathrm{I}}_9$ for convenience. The new substages confirmed were labeled ${\mathrm{I}}_2$, ${\mathrm{I}}_7$, and ${\mathrm{I}}_9$. Substage ${\mathrm{I}}_2$ occurs at 22-23°K and represents 1.5-2% recovery. Substage ${\mathrm{I}}_7$ occurs at 45°K, is dose-dependent, and appears more clearly resolved after the higher energy irradiations. This substage, ${\mathrm{I}}_7$, may correspond to the "bump" found at about 50°K by Nilan and Granato. ${\mathrm{I}}_9$ occurs at 53-59°K, represent 1% recovery and appears to be dose-dependent. ${\mathrm{I}}_9$ occurs near the temperature of the ${\mathrm{II}}_a$ substage reported by Sosin and Neely for doped copper. The shape of the isochronal derivative on the high-temperature side of ${\mathrm{I}}_5$ (${\mathrm{I}}_D$ former notation) indicates that another substage, ${\mathrm{I}}_6$, 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 ${\mathrm{I}}_B$ and ${\mathrm{I}}_C$ (former notation) as a function of bombarding electron energy, supports the conclusion that not much change in population of ${\mathrm{I}}_B$ or ${\mathrm{I}}_C$ occurs beyond $E=1.2\mathrm{}$ MeV.