Shockwave and spallation in silver and other materials by sub-ns laser pulse at 10^16 W/cm^2 intensity

The laser spallation effect due to intense shockwaves caused by a brief and intense laser pulse irradiating a target surface, 2 mm thick, has been investigated for silver and other materials. For 300 ps IR laser pulse, at intensities of the order of 10(16) W/cm(2), the shockwave may produce deformations of the back-face in ductile materials, such as Ag, Cu and Al. In heavy materials with high tensile strength, such as Ta, the shockwave produces cracks in the bottom of the laser crater but not deformation in the back-face, while in brittle materials, such as monocrystalline Ge, it produces only superficial cracks and flaking, but not deformation and spallation of the back-face. In thick polymeric materials, such as high-density polyethylene, the ablated crater shape is well defined and the shockwave is strongly damped, and no deformation has been observed in the back-face. The laser ablation yield and the ion acceleration in the backward direction have been measured by mass lost and time-of-flight measurements. SEM microscopy of the different irradiated targets, showing details of the crater size, edges, flaking and deformation in the back-face, useful for a discussion on the shockwave propagation and shock pressure calculation, is presented

Protons and carbon ions acceleration in the target-normal-sheath-acceleration regime using low-contrast fs laser and metal-graphene targets

fs pulsed lasers at an intensity of the order of 1018 W/cm2, with a contrast of 10−5, were employed to irradiate thin foils to study the target-normal-sheath-acceleration (TNSA) regime. The forward ion acceleration was investigated using 1/11 µm thickness foils composed of a metallic sheet on which a thin reduced graphene oxide film with 10 nm thickness was deposited by single or both faces. The forward-accelerated ions were detected using SiC semiconductors connected in time-of-flight configuration. The use of intense and long pre-pulse generating the low contrast does not permit to accelerate protons above 1 MeV because it produces a pre-plasma destroying the foil, and the successive main laser pulse interacts with the expanding plasma and not with the overdense solid surface. Experimental results demonstrated that the maximum proton energies of about 700 keV and of 4.2 MeV carbon ions and higher were obtained under the condition of the optimal acceleration procedure. The measurements of ion energy and charge states confirm that the acceleration per charge state is measurable from the proton energy, confirming the Coulomb–Boltzmann-shifted theoretical model. However, heavy ions cannot be accelerated due to their mass and low velocity, which does not permit them to be subjected to the fast and high developed electric field driving the light-ion acceleration. The ion acceleration can be optimized based on the laser focal positioning and on the foil thickness, composition, and structure, as it will be presented and discussed

Nanoparticles: Production, Characterization and Applications

The production of metallic nanoparticles using pulsed laser ablation in water is presented. The physical characterization of the produced nanoparticles is reported in terms of electronic microscopy, optical and mechanical properties, SPR, EDX, XPS and XRD spectroscopies. The applications of the prepared nanoparticles involve different scientific fields. In particular will be discussed their use to modify some properties of polymers, liquids and alloys. Special attention is devoted to the use of nanoparticles for polymeric laser welding, to the use as an image contrast medium in the biological environment and to the use of Au-NPs targeting for radiotherapy of cancer tissues

Conductor losses calculation in two-dimensional simulations of H-plane rectangular waveguides

This paper presents a novel numerical approach to simulate H-plane rectangular-waveguide microwave circuits considering a reduced quasi-2D simulation domain with benefits for computational cost and time. With the aim to evaluate the attenuation of the full height 3D component, we propose a modified expression for the waveguide top/bottom wall conductivity. Numerical 2D simulations are validated against results from full wave 3-D commercial electromagnetic simulator. After a benchmark on a simple straight waveguide model, the method has been successfully applied to an asymmetric un-balanced power splitter, where an accurate power loss prediction is mandatory. Simulation time and memory consumption can be reduced by a factor ten and seven respectively, in comparison with complete 3D geometries. Finally, we show that, also for quasi-2D E-bend waveguide, a case where the translational H-plane symmetry is broken, the error on conductor losses computation is mitigated by our approach since the method remains still valid in a first approximation

Laser ablation coupled to mass quadrupole spectrometry for analysis in the cultural heritage

A Nd:YAg laser operating at 1064 nm, 150 mJ, 3 ns pulse duration, 1-10 Hz repetition rate and 109 W/cm2 intensity is employed to irradiate ancient metallic and ceramic samples in high vacuum. A mass quadrupole spectrometer (MQS), operating between 1-300 amu with sensitivity better than 0.1 ppm, analyzes elements and compounds. Repetitive laser ablation removes in controlled manner the first surface layers of the irradiated samples so that the irradiation time can be correlated to the layer depth. MQS can be fixed to peculiar masses so that during the laser irradiation the mass yields can be plotted as a function of the sample depth. The technique permits to give the depth profiles of elements, chemical compounds and isotopes characterizing the composition of the analyzed samples. The analysis of ancient coins based on bronze and silver alloys and of old vitrified colored ceramics has been investigated to identify peculiar elements of the colored layers. Particularly, the lead isotopic ratios 208Pb/207Pb and 206Pb/207Pb were measured in bronze coins. Measurements were compared with the database of lead isotopic ratios in lead minerals extracted from old mines in the Mediterranean basin. In some cases, of special interest for Archeologists, the comparison has indicated that the lead employed for the coin production could have been extracted from mines of particular geographic sites. © Published under licence by IOP Publishing Ltd

A comparative analysis of old and recent Ag coins by XRF methodology

The investigation of silver coins dated since the first century B.C. up to recent times, coming from different countries in the world, has successfully generated a growing interest among numismatic researchers. The classification of these coins into originals, copies and imitations - according to their provenance and to their Ag content - has been performed by using the X-ray fluorescence (XRF) analysis. The archaeological challenge is to explain the large diversification of these coins, to determine the differences in composition, weight and physical aspects. A non-destructive physical method was employed to study the properties of silver coins (as in this case) allowing a detailed characterization of the analyzed samples. The XRF analysis was applied to the bulk, through an X-ray tube, and to the surface patina, through an electron beam

Effects of long term application of compost and poultry manure on soil quality of citrus orchards in Southern Italy.

A six-year study was carried out in an organically managed orange orchard located in Sicily (Southern Italy) to assess the effect of compost and organic fertilizers utilisation on soil quality. Adopting a randomized-block experimental design with three replicates, four treatments were carried out. In treatments 1 and 2, two different composts (C1 from distillery by products and C2 from livestock wastes) were applied. The plots of treatment 3 were fertilized using dried poultry manure. The control treatment was fertilized with mineral/synthetic fertilizers. In order to verify the hypothesis that composts and organic fertilizers improve soil fertility, soil quality was evaluated by selecting dynamic soil parameters, as indicators linked to C and N cycles. Total organic C, total N, C/N ratio, humified fraction, isoelectric focusing (IEF) of extracted organic matter, microbial biomass C, potentially mineralisable N under anaerobic conditions, potenzially mineralizable C, C mineralization quotient and metabolic quotient were determined for each sample. Furthermore, the Comunity level Physiological Profile (by Biolog tecnique) was defined, calculating derived functional biodiversity and versatility indexes. Parameters related to IEF and potentially mineralizable C showed significant differences among the treatments. Moreover, total C, total N and humification parameters tended to increase, while no differences were observed in biodiversity indexes. On these findings, it was concluded that composts and poultry manure only weakly affected soil properties, though they increased soil nutritive elements potentially available to crops