Heavy ion-induced deformation of radiation-amorphized U 3Si

Abstract

Ten micrometre thick U 3Si layers were amorphized by ion bombardment with 250 MeV Xe ions at room temperature. Subsequently these layers were post-irradiated with either 250 MeV Xe ions or 120 MeV Kr ions below 100 K at a beam incidence angle of 45°. After irradiation, the surface morphology was examined at room temperature by optical microscopy. At small fluences the surface of amorphous U 3Si revealed a displacement in direction of the projection of the ion beam onto the surface. At larger fluences a ripple structure developed. The observations can be understood as consequences of a shear flow released by the formation of fluid ion tracks. From the experimental data an electronic energy loss threshold of 19 keV/nm is deduced for the formation of such tracks in amorphous U 3Si. Obviously, for estimating the in-pile damage the electronic energy loss of fast fission fragments cannot be ignored.