A comparison of initial damage rates due to electron and neutron irradiations measured by internal friction techniques. I. Flux and temperature dependencies; scaling law

The initial pinning rate of dislocations, as computed from changes in Young’s modulus, was measured in high-purity polycrystalline copper during electron and neutron irradiations. For the same sample, flux and temperature dependencies of the pinning rate were studied for irradiations by 14.1-MeV neutrons and 1.0- and 0.5-MeV electrons. For a temperature of 330 K, the initial pinning rate depended on the flux to the 0.89±0.2 power in contradiction of simple kinetics. Additionally, to duplicate a given pinning rate due to a 14.1-MeV neutron flux between 1011 and 1012 m−2 s−1, a 0.5-MeV electron flux of 21.7±0.7 or a 1-MeV electron flux of 2.2±0.1 times the neutron flux was necessary. Temperature dependence studies from 310 to 390 K showed the same dependence for neutron and electron irradiations. The difference in migration energies in the lattice and along the dislocations was found to be 0.18±0.02 eV over this temperature range. The copper sample exhibited the Simpson-Sosin peaking of the decrement during all irradiations. The above observations lead us to conclude that the same defect, the interstitial, is responsible for pinning during both electron and neutron irradiation.