X-ray characterization of picosecond laser plasmas

Abstract

Short-lived plasmas, produced by focussing a 0.58 μm, 1 ps, 1 mJ dye laser beam to 10 13–10 14W cm -2 onto solid planar targets, are diagnosed by a photoconductive detector, pinhole camera, X-ray stream camera and by shadowgraphy. 1–5% conversion efficiency to a <20 ps XUV and X-ray burst is demonstrated using high Z (> 40) targets at 1–2 × 10 14W cm -2. Electron temperatures of 200 eV and higher are deduced from spatially resolved absolute X-ray yields. The heated material depth for carbon is measured to be 200 Å, corresponding to a low intensity optical depth of one. The quasi point-like nature of > 1 keV X-rays from these plasmas is used to image a 20 μm diameter wire with 3000 Å resolution in one dimension.