Plasma Production via 6 ns Pulsed Laser at 1064 and 532 nm wavelengths on Nanostructured Targets

This thesis presents the result of a study, within the scope of the PLANETA experiment (an INFN research program), on the effect of nanostructures on laser-matter interaction. Specifically, the plasma created on targets containing metal nanowires when irradiated with a laser pulse 6 ns long, at 1064 and 532 nm wavelength, with a power density of about 1 · 1012 W/cm2 . Laser-produced plasma is of interest for a wide range of scientific and technological application, from using them as a source of X-rays to the possibility of nuclear fusion thanks to the high densities and temperatures which can be reached inside the plasma. However, most applications are constrained by the very limited penetration of laser energy into matter, due to the rapid formation of a reflective critical surface of dense plasma. PLANETA experiment was meant to investigate if targets with metal nanowires (thin cylinders with diameter < 100 nm, smaller than the laser’s wavelength) could lead to production of a hotter and/or longer lived plasma compared to bulk metal. The proposed mechanism would be a deeper penetration of laser light into the targets. This could lead to volumetric, instead of superficial heating, and thus to the production of a hotter and denser plasma compared to a bulk metal target. Targets were produced at the electron microscopy lab of INFN Bologna, with nanowires of different geometrical parameters and different metals. They were irradiated with a Nd-Yag laser at the INFN Laboratori Nazionali del Sud in Catania, and the resulting plasmas were observed with detectors of several kinds to compare them with plasmas from bulk metals. A different INFN facility at the Department of Physics, University of L’Aquila, equipped with a 532 nm wavelength laser was available to the PLANETA experiment.