Application of laser-induced double ablation of plasma for enhanced macroparticle acceleration

Abstract

The objective of the studies was to demonstrate that using laser-induced double plasma ablation (created by the laser light and the X-rays from a high-Z dopant introduced to a low-Z target) it is possible to increase significantly the kinetic energy of a macroparticle accelerated by a laser. In the experiments, the high-intensity (1014 — 1015W/cm2), high-energy (up to 120J) sub-ns 3ω beam of the PALS laser interacted with various (with and without high-Z dopant) thin foil targets. The laser-driven foil (the ‘macroparticle’) collided with a massive (A1) target producing crater, the volume of which was a measure of the foil kinetic energy released to the foil. Parameters of the accelerated foil and the ablated plasma were determined using three-frame interferometry, ion diagnostics, soft and hard X-ray diagnostics as well as the measurements of the crater dimensions. The results of investigations for low-Z foil targets; for undoped (homogenous) and for ones with high-Z dopants, were compared. It was found that the X-ray yield from the foil target with high-Z dopant is a few times higher than that from the undoped target and the ablating plasma flow is faster and more collimated. It results in an increase in kinetic energy of the accelerated foil (the crater volume is up to 80% larger) provided that the foil is sufficiently thick (20μm). Higher increase in the kinetic energy seems to be possible when using foils with a higher amount of a high-Z dopant and the foil thickness is well matched to the laser beam parameters.