Angular distributions of ions from laser-produced plasma

Abstract

This paper presents comprehensive experimental results of angular distributions of ions emitted from laser-produced plasmas. Performing a series of laser shots onto planar Sn, Au, and Pb targets, both the focusing conditions as well as the tilt angle of the target were changed to study the effect on the plasma expansion. In the experiments, the iodine laser system PERUN (laser energy of 30 J in 350 ps of duration) with laser power density of 5 × 10¹⁴ W/cm² was used. For plasma diagnostics four ion collectors and an ion-energy analyzer were applied. Comparison of angular distribution of the fast ion group (velocity within the range of 1–3.4 × 10⁸ cm/s) and of the slow ion group (velocity within the range of 0.14–1 × 10⁸ cm/s) shows distinct differences. The preferred direction of ion emission of these groups depends seriously on focusing conditions. When setting the focus on the in-focus position both groups of ions are peaked in the direction close to the target normal. The maximum charge of ions registered by the ion-energy analyzer were 36+, 51+, and 49+ for Sn, Au, and Pb, respectively.