Acceleration of carbon ions in a skin-layer interaction regime in laser ablation experiments

Abstract

ABSTRACT The regime of skin-effect interaction was proposed as the mechanism of ion acceleration, and the range of validity of theskin-effect mode was established. The results are illustrated on laser evaporation of graphite with Nd:YAG laser (1.064.tm), KrF laser (248 nm) and ArF laser (193 nm). The UV lasers the interaction has a bi-modal nature: the interaction mayproceed initially in the skin effect regime resulting in a few high-energy ions, until the hydrodynamics expansion begins atthe later stage. The skin-effect interaction at the initial stage of UV laser pulse gives the first, to our knowledge, explanation for acceleration of ions up to —1 00 eV at the low laser intensities I 08..1 0 W/cm2 and ns-range pulse duration. Keywords: Laser ablation; skin-effect interaction; ion acceleration; carbon vapours; laser plume diagnostics. 1. INTRODUCTION Laser ablation of graphite targets has been generally used recently for deposition of thin nanocrystalline and amorphousdiamond-like carbon films'' and for production of nanostructured materials such as carbon nanotubes5'6, and carbonnanofoam7. In this paper we concentrate on defining the properties of atomic vapours and plasma formation for laser