Ultra short - time dynamics of radiation damage in fcc metals

We have performed molecular-dynamics simulations of displacement cascades in copper in order to investigate the non-equilibrium ultra-short time damage and to evaluate the possibility of observing it experimentally in-situ (e.g. in a pump/probe laser experiment). The atomic trajectories have been analysed by calculating their X-ray diffraction patterns as a function of time. The results show that an integrated X-ray intensity can indeed be used to evidence the irradiation effects. Even though the number of Frenkel defects is large, the main effect of the irradiation showing up in the X-ray intensities at ultra-short times is an important alteration of the lattice vibrations. On the basis of these results, a new pump/probe set-up is proposed.