Abstract
In this study, the effect of pore size in the opaque poly(methyl methacrylate) and its composition is investigated by optical measurements as well as Rutherford Backscattering Spectroscopy and Elastic Recoil Detection Analyses. The enhancement of the absorption coefficient induced by the presence of micrometric beads makes these porous thin foils high absorbent to IR radiation and suitable to be laser irradiated in order to generate a hot plasma rich in proton emission. The presented results indicate that the high optical transparency of PMMA foils can be strongly reduced by the presence of the micrometric acrylic beads and that the presence of high Z-metallic nanoparticles, such as gold, embedded in the polymer enhances the acceleration of emitted ions. The fabricated advanced targets have been irradiated by lasers at low intensity (Messina University) and at high intensity (PALS Research Infrastructure in Prague) generating plasma accelerating high proton yield and energy.
Highlights
Advances in polymeric processing have attracted growing interest from fundamental and experimental point of view, especially concerning the fabrication of micro and submicro-scale materials
Special attention to the polymer structure comes from their high content of hydrogen and carbon atoms, and by the optical properties, which play an important role in case thin polymeric foils are used to generate nonequilibrium plasma by laser pulse and consequent ion acceleration
Hot plasma rich in protons and carbon ions can be obtained irradiating in vacuum thin polymeric foils by high intensity laser pulses
Summary
Advances in polymeric processing have attracted growing interest from fundamental and experimental point of view, especially concerning the fabrication of micro and submicro-scale materials. Thin polymeric films can be used to accelerate protons by laser impact from target-normal-sheathacceleration (TNSA) regime using intensities higher than 1015 W/cm2 [1] The drawback of this procedure consists in the too low laser absorption due to the limited thickness and high transparency of the polymer foil. In this way, a significant advantage of its use consists in the transformation of the polymer structure in a high absorbent opaque film to generate high laser absorption, transforming the energy of the deposited coherent photons into kinetic energy of electrons, protons and other particles. It is worthy to mention as the growth of the crystalline regions, induced by temperature gradient can be responsible for the generation of quasispherical aggregates with size ranging between 1 μm and 10 μm [3]
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