On the highly directional expansion of laser-produced plasmas

Abstract

The expansion of plasmas produced by focusing a CO₂ laser pulse onto solid planar targets is discussed. The plasmas are studied using an extreme ultraviolet spectroheliograph. With titanium and iron targets the plasma blow-off observed in transitions within highly ionised species (e.g. Fe XVI) occurs parallel to the target normal. The plasma is tightly confined to narrow cylindrical structures about 0.7 mm in diameter, and is observed as far as 1 cm from the target surface. The electron density is about 2.8*10¹⁸ cm^-3 at a distance of 0.7 mm from the target surface and decreases to approximately 6.5*10¹⁷ cm^-3 at a distance of 2.9 mm from the surface.