Erosion of copper target irradiated by deuterium ion beam with ultimate fluence is studied. The target originally destined for neutron generation represents bulk copper substrate covered by 3-mum titanium layer. The target was irradiated by deuterium
ion beam generated in Bayard-Alpert type ion source with energy of ions 17.5 keV/nuclear. Maximal fluence in the center of the target achieves 2.5x10^23atoms/cm^2. Measurements of the profile of irradiated target and estimation of fluence shows that physical sputtering is a dominating process that determines the target erosion Most interesting feature is growth of mum-size tadpole-shaped structures, localized in the cracks of the surface. RFA analysis of these structures showed extremely large (up to 60%at.) carbon content.
