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Nanostructured targets for TNSA laser ion acceleration

Torrisi L., Calcagno L., Cutroneo M., Badziak J., Rosinski M., Zaras-Szydlowska A., Torrisi A.

Nukleonika

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2016

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Vol. 61, No. 2

103--108

EN

Nanostructured targets, based on hydrogenated polymers with embedded nanostructures, were prepared as thin micrometric foils for high-intensity laser irradiation in TNSA regime to produce high-ion acceleration. Experiments were performed at the PALS facility, in Prague, by using 1315 nm wavelength, 300 ps pulse duration and an intensity of 1016 W/cm2 and at the IPPLM, in Warsaw, by using 800 nm wavelength, 40 fs pulse duration, and an intensity of 1019 W/cm2. Forward plasma diagnostic mainly uses SiC detectors and ion collectors in time of fl ight (TOF) confi guration. At these intensities, ions can be accelerated at energies above 1 MeV per nucleon. In presence of Au nanoparticles, and/or under particular irradiation conditions, effects of resonant absorption can induce ion acceleration enhancement up to values of the order of 4 MeV per nucleon.

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Multi-energy ion implantation from high-intensity laser

Cutroneo M., Torrisi L., Ullschmied J., Dudzak R.

Nukleonika

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2016

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Vol. 61, No. 2

109--113

EN

The laser-matter interaction using nominal laser intensity above 1015 W/cm2 generates in vacuum non- -equilibrium plasmas accelerating ions at energies from tens keV up to hundreds MeV. From thin targets, using the TNSA regime, plasma is generated in the forward direction accelerating ions above 1 MeV per charge state and inducing high-ionization states. Generally, the ion energies follow a Boltzmann-like distribution characterized by a cutoff at high energy and by a Coulomb-shift towards high energy increasing the ion charge state. The accelerated ions are emitted with the high directivity, depending on the ion charge state and ion mass, along the normal to the target surface. The ion fluencies depend on the ablated mass by laser, indeed it is low for thin targets. Ions accelerated from plasma can be implanted on different substrates such as Si crystals, glassy-carbon and polymers at different fluences. The ion dose increment of implanted substrates is obtainable with repetitive laser shots and with repetitive plasma emissions. Ion beam analytical methods (IBA), such as Rutherford backscattering spectroscopy (RBS), elastic recoil detection analysis (ERDA) and proton-induced X-ray emission (PIXE) can be employed to analyse the implanted species in the substrates. Such analyses represent ‘off-line’ methods to extrapolate and to character the plasma ion stream emission as well as to investigate the chemical and physical modifications of the implanted surface. The multi-energy and species ion implantation from plasma, at high fluency, changes the physical and chemical properties of the implanted substrates, in fact, many parameters, such as morphology, hardness, optical and mechanical properties, wetting ability and nanostructure generation may be modified through the thermal-assisted implantation by multi-energy ions from laser-generated plasma.

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Proton emission from laser - generated plasmas at different intensities

Torrisi L., Cutroneo M., Cavallaro S., Giuffrida L., Margarone D.

Nukleonika

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2012

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Vol. 57, No. 2

237-240

EN

Proton acceleration from laser-generated plasma is carried out at intensities ranging between 1010 and 1019 W/cm2, by using ns, ps and fs laser systems. The high energy density transferred from the pulsed laser beam into the solid target generates ionized species released in vacuum from the solid surface. Fast electrons followed by slower ions build up a double-layer and a consequent electric field, which is responsible for the ion acceleration mainly along the target-normal. Polymeric targets containing nanostructures (or metallic species) with high laser absorbing capacity, and metallic hydrates (or H-enriched metals), permit to increase the plasma temperature and density, thus to improve the proton beam energy and current. Thick targets and low laser intensities, operating in repetitive pulse, allows to generate high currents of low energy protons. On the other hand, through the use of thin targets and high laser intensities enabled the generation of high proton energies, above 1 MeV.