F. Paladini

Modification of polymer characteristics by laser and ion beam

In this work, two different techniques to modify polymeric surfaces are compared: laser irradiation and ion implantation. The treated polymers were samples of ultra high molecular weight polyethylene. The irradiation treatment was performed by utilizing two different laser sources operating in the UV and IR range by applying many laser shots in an air atmosphere. Ion implantation was performed using a new laser ion source accelerator with an accelerating voltage of 40 kV. Contact angle, roughness and Fourier transform infra red measurements were carried out before and after the treatments in order to compare surface characteristics. An increase of the wettability and roughness was observed when using UV laser treatment, while an increase of the hardness was obtained by ion implantation.

Comparison of the laser effects induced on ultra-high-molecular-weight polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE) is a versatile polymer employed in many fields for its good chemical–physics characteristics. In particular, it is widely utilized in biomedical fields due to its high degree of biocompatibility and its easy control on wettability of the surface. In this work, the laser radiation has been utilized to effect different degrees of change to the wettability characteristics of the UHMWPE depending on the laser used. The wettability modification was investigated by measuring the contact angles using the sessile drop method. It was observed that the interaction with laser wavelengths at 1064 and 532 nm effected very little change in the wettability characteristics of UHMWPE. On the contrary, the interaction of UHMWPE with 248 and 308 nm laser wavelengths resulted in a marked improvement in the wettability characteristics of the polymer; in particular, the UHMWPE irradiated by 308 nm, after 10 laser shots, reported a linearly increasing of the polymer wettability.

High magnetic pulse by solenoids for intense ion beam transport

A high voltage pulser up to 50 kV, with a main pulse of 2 μs time duration, was realized using a fast high voltage capacitor of 150 nF (50 kV) connected to the ground by a homemade spark-gap. The circuit, contained in a metallic box to avoid irradiation, had short electric connections in order to reduce the inductances. The diagnostic was performed by two systems: a self-integrating Rogowski coil and an integrator connected to a current transformer, both suitable for pulses longer than 1 μs. To focus ion beams with energy reaching 40 keV, we made two solenoids having an inductance of 3.6 and 16 μH which were fed by the current generated by the pulser up to 12 kA, 1 μs at 50 kV of charging voltage of capacitor. The measurements determined a magnetic field at the solenoid center of 0.61 T for the more inductive solenoid and 1.14 T for the other one.

A study of the secondary electrons yield produced by laser induced ions on Faraday cups as a function of beam angle

We analyze the dependence of the Secondary Electron Emission yield on the beam incidence angle (θ) in the case of Faraday cups used for diagnosis of laser-plasma. We show that this dependence follows a secα(θ) law, consequently θ ≠ 0 situations (i.e. non-normal incidence) should be treated with care to avoid wrong measurements.

High voltage pulse of short duration to feed solenoids for intense ion bean transport

A high voltage pulser up to 50 kV, with a main pulse of 2

Polymer processing by a low energy ion accelerator

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Misure di assorbimento di raggi X per la determinazione degli spessori delle corone d'oro del Museo "MArTA" di Taranto

s time duration, was realized using a fast high voltage capacitor of 150 nF (50 kV) connected to the ground by a homemade spark-gap. The circuit, contained in a metallic box, had short electric connections in order to reduce any stray inductances. The diagnostics was performed by two systems: an auto-integrating Rogowski coil and an integrator connected to a current transformer, both suitable for pulses longer than 1

Bobina di Rogowski lineare

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The restoration of the Colosso di Barletta: EDXRF analysis

s. In order to get the above characteristic the Rogowski coil circuit must have a ratio L/R higher than 1

Study of Faraday cups for fast ion beams provided by a LIS source

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