Target normal sheath ion acceleration by fs laser irradiating metal/reduced graphene oxide targets

Abstract

Target normal sheath ion acceleration is applied with a high contrast fs laser irradiating advanced targets based on thin metallic films (Al, Cu, Ag and Au) covering micrometric foils of reduced graphene oxide (rGO). The laser intensity is of about 10 18 W/cm 2 and the laser focal position with respect to the target surface is optimized to have the maximum proton acceleration. Plasma diagnostics are investigated using time-of-flight technique employing SiC detectors, ion collectors, and gaf-chromic films. Micrometric aluminum absorbers were employed to separate the faster proton detection by other accelerated ions. At the optimized laser focal position, the maximum proton acceleration of 2.5 MeV and 3.0 MeV energy was obtained using Ag(200 nm) and Au(200 nm) covering rGO(7 µm) targets, respectively. The high proton energy is due to the high electrical and thermal conductivity and high mechanical resistance of the used rGO foils and to the high plasma electron density of the target. K: Plasma diagnostics -charged-particle spectroscopy; Plasma diagnostics -probes; Plasma generation (laser-produced, RF, x ray-produced) 1Corresponding author.

2.5‐MeV neutron source controlled by high‐intensity pulsed laser generating plasma

“…F I G U R E 2 Deuterium-deuterium and deuterium-tritium cross-sections versus the deuterium projectile energy The plasma enriched in protons was obtained by irradiating polymers, polymers with thin Au films, polymers with metallic nanoparticles, and carbon nanostructured films containing carbon nanotubes and graphene. [36,37] Polyethylene, in fact, contains more than 66% hydrogen in atomic composition and permits the release in plasma of high proton charges. The use of nanoparticles for enhancing the surface/volume ratio permits conferring high hydrogen absorption at the metal-polymer interface, showing a double plasma advantage, to produce high proton fluxes and high proton acceleration, thanks to the higher effective atomic number of the target due to the insertion of heavy metallic nanoparticles, such as Au, in the polymer, at concentrations of the order of 1 wt%, which increases the electron plasma density and consequently the electric field driving the ion acceleration.…”

“…[38] The use of a target of graphene oxide and carbon nanotube is because they absorb a large quantity of hydrogen, which can be released as accelerated protons, as reported recently. [37] 2 EXPERIMENTAL SET-UP…”