Laser ion acceleration using a solid target coupled with a low density layer

TL;DR

This study uses particle-in-cell simulations to show that adding a low density near-critical layer to a solid target significantly enhances laser-driven proton acceleration by increasing electron energy and electric fields.

Contribution

It demonstrates that multilayer targets with a near-critical foam layer improve proton acceleration efficiency and maximum energy compared to bare solid targets.

Findings

Maximum proton energy up to three times higher with foam layer

Enhanced electron acceleration and electric field formation

Improved conversion efficiency of laser energy to particle energy

Abstract

We investigate by particle-in-cell simulations in two and three dimensions the laser-plasma interaction and the proton acceleration in multilayer targets where a low density "near-critical" layer of a few micron thickness is added on the illuminated side of a thin, high density layer. This target design can be obtained by depositing a "foam" layer on a thin metallic foil. The presence of the near-critical plasma strongly increases both the conversion efficiency and the energy of electrons and leads to enhanced acceleration of proton from a rear side layer via the Target Normal Sheath Acceleration mechanism. The electrons of the foam are strongly accelerated in the forward direction and propagate on the rear side of the target building up a high electric field with a relatively flat longitudinal profile. In these conditions the maximum proton energy is up to three times higher than in the case of the bare solid target.