Multiscale modeling of radiation damage: applications to damage production by GeV proton irradiation of Cu and W, and pulsed irradiation effects in Cu and Fe

The damage accumulation in Cu and W is investigated using a multiscale modeling approach. The efficiency for defect production of displacement cascades is calculated using molecular dynamics (MD). The simulation uses the recoil spectra from spallation reactions of 1.1 and 1.9 GeV protons as calculated with the Los Alamos High Energy Transport (LAHET) nuclear transport code. The total number of defects produced under these irradiation conditions is obtained both from the NRT and MD approximations. The value for the change in electrical resistivity produced by the irradiation-induced defect microstructure is compared to experimental values obtained from irradiations with protons of the above energies, showing a better agreement for the lower irradiation energy. The damage evolution is simulated with kinetic Monte Carlo, where the inputs for the calculation are the results from MD previously obtained. A large recovery of the damage is found at room temperature as a result of the migration of interstitial clusters, single vacancies and small vacancy clusters to sinks such as dislocations. Finally the effects of pulsed irradiation have been analyzed in Cu and Fe with similar simulation tools. The results indicate a clear influence of pulsing at 1 Hz, but not at higher frequencies.