NEAR-THRESHOLD ABLATION OF TARGET MATERIAL IRRADIATED WITH PULSED ION-BEAMS

The process of target ablation induced by pulsed ion beams is investig ated. The beam power density of 0.01-0.1 GW/cm(2) is around the sublim ation energy of the target material. The thickness of the layer to be removed from the target is estimated from the temperature distribution calculated numerically with a diffusion equation. The emitted particl es are collected with C collectors, which are later subjected to RES a nd SEM/EPMA analyses. It is found that ablated particles forming a fil m on the collector amount to only 10% of the target atoms within the m aximum range of the ions, while a significant amount of the ablated ma terial is observed as macroscopic particles with equivalent diameters up to several tens of micrometers. TOF measurements of the ablation pl ume together with RES measurements of thin-film targets after irradiat ion suggest that the formation of the film is predominated by vaporiza tion from the surface of the ablated mass, which is recondensed on the collector before completing the vaporization.