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A Pulsed ns laser operating at 532 nm wavelength with 150 mJ pulse energy was employed to irradiate micrometric thick mylar films, from 1 to 100 μm thick, covered by 0.05 μm Au in the back face. Protons and light ions have been accelerated by the electric field developed in the non‐equilibrium plasma by the laser pulse in a vacuum at an intensity of the order of 1010 W/cm2. Time‐of‐flight technique, obtained using a Faraday cup and a fast storage oscilloscope, is employed to measure the ion velocity, energy, and yield emitted in backward and forward directions. The yield of the emitted plasma photons is also evaluated. Two ion collectors are used in opposite directions to measure the plasma radiations emitted in backward and forward directions. Data analysis is based on the Coulomb‐Boltzmann‐shifted (CBS) distribution function. The target ablation yield is evaluated in the order of 3.5 μm per laser shot. [ABSTRACT FROM AUTHOR]

The time-dependent graphene oxide (GO) reduction in medium vacuum under ultraviolet (UV) irradiation at 365 nm has been investigated. We found that GO exposed to UV at room temperature and at a vacuum of about 10−1 mbar shows a notable oxidation for irradiation times up to about 60 min followed by a successive reduction up to 210 min. Characterization measurements have been performed mainly using the Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) and Raman spectroscopies. ATR-FTIR spectra, acquired in the (400–4000) cm−1 wavenumber range, have indicated an initial decrement of the IR transmission (oxidation process) with the exposure time up to about 60 min and a successive increase of the IR transmission (reduction process) for greater irradiation times up to 210 min. The IR transmission bands are attributed to the oxygen functional groups contained in GO which increase for low UV exposure times and gradually disappear during the UV-induced reduction process. Raman spectra confirm this interpretation showing a decrease of the AD/AG ratio value, with respect to the GO virgin value, for low UV exposure times and an increase for greater times. The GO oxidation and reduction processes, due to the UV GO treatment in medium vacuum conditions, have been also verified by energy dispersive X-ray fluorescence and surface wettability measurements. [ABSTRACT FROM AUTHOR]

Polymethylmethacrylate (PMMA) has been irradiated by 365 nm UV wavelength at different exposition times in air and room temperature. The macromolecular modifications induced in the polymer have been investigated using attenuated total reflectance (ATR) coupled to Fourier transform infrared (FTIR) spectroscopy, UV-Visible spectroscopy, surface profiler, wetting ability, and electronic microscopy. The observed chemical, optical and morphological changes occurred as a consequence of the UV irradiation suggest that chain scissions are induced by the UV radiations, with reduction of the IR and visible transmittance, wetting ability and surface roughness. The study of the degradation of PMMA by different times of exposure to UV radiation is investigated with the aim of understanding the effects produced over time on optical devices such as intraocular lenses, optical fibres, protective screens, and instrumental lenses. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets/polydimethylsiloxane (GNPs/PDMS) nanocomposites foils are obtained by dispersing nanoplatelets of graphene (GNPs) into polydimethylsiloxane (PDMS) at a given GNPs concentration but at different curing times to study the effects of curing time on some their bulk and surface properties. Their appearance and morphology have been examined by optical and scanning electron microscopies, their wettability and roughness by the sessile drop method and profilometry, their bonds by µRaman and ATR-FTIR spectroscopies, their dielectric response by dielectric spectroscopy. In particular, optical and SEM images and roughness measurements indicate a roughened and hydrophobic surface at the shortest curing time that becomes less roughened, more uniform and less hydrophobic as curing time increases. ATR-FTIR and µRaman spectra reveal the absence of chemical interaction between GNPs and PDMS. The behavior of the PDMS real and imaginary parts of dielectric permittivity without and with GNPs and at increasing curing times seems to define the obtained GNPs/PDMS nanocomposites as low-loss materials. The obtained results show that the curing time significantly affects the filler distribution in the PDMS matrix and consequently the properties of the final nanocomposites. [ABSTRACT FROM AUTHOR]

A ns-pulsed laser operating at 532 nm wavelength has been employed to irradiate micrometric mylar films (1–100 μm) with an attached 0.1 μm Al film on its back face. Protons and light ions have been accelerated by the electric field developed in the non-equilibrium plasma generated by the laser pulse in a vacuum at an intensity of the order of 1010 W/cm2. The Time-of-flight (TOF) technique, using a Faraday cup (ion collector) coupled to a fast storage oscilloscope, has been employed to measure the ion velocity, energy and yield. The yield of plasma-emitted photons has been also evaluated. Two ion collectors have been used in opposite directions to measure the maximum ion acceleration by the TOF data acquired in backward and forward directions and the photon yield as a function of the target thickness. The evaluation of the ion energy distribution has been based on the Coulomb-Boltzmann-Shifted (CBS) distribution function. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) thin foils were deposited on silicon and aluminum substrates and then irradiated in vacuum with 300 keV helium and argon ion beams at room temperature and at fluences ranging between 5 × 1014 ions/cm2 and 1016 ions/cm2. Attenuated total reflectance (ATR) coupled to the Fourier-transform infrared (FTIR) spectroscopy, μ-Raman spectroscopy, X-ray diffraction (XRD) and other analyses, such as Rutherford backscattering (RBS) of alpha particles, energy-dispersive X-ray (EDX) fluorescence, elastic recoil detection analysis (ERDA), scanning electron microscopy (SEM) and contact angle measurements, were used to study the effect of ion irradiation in GO. Such analytical techniques have indicated that the Ar ion implantation at high fluence may induce diamond-like-carbon (DLC) phases in the superficial irradiated layers. ATR-FTIR spectroscopy has evinced a partial removal of the oxygen functional groups with the ion fluence, indicating a GO reduction, and the presence of C=C chemical bonds when Ar irradiation is employed. Raman spectra analysis has pointed out a different behavior of GO by changing the type of ion. In fact, irradiation with 300 keV He ions induced a gradual GO reduction which increased with fluence, while the 300 keV Ar ions implantation also produced DLC, whose formation was promoted by the high energy release into GO from the Ar ions. The presence of some diamond-like crystalline phases onto the surface of the GO foil irradiated with 300 keV Ar+ ions at a fluence of 1016 ions/cm2 is also indicated by XRD spectra. RBS and EDX analyses confirm the beam-induced GO reduction from the C/O atomic ratio deduced value that grows with the He and Ar irradiations and assumes, at the same beam fluence, the highest value with the Ar+ ions. The highest carbon concentration in the Ar-irradiated rGO surface is also indicated by SEM images. The minor presence of hydrogen in the reduced GO foils has been evinced by ERDA spectrometry according to which this reduction is stronger for the Ar ion irradiation. At the highest irradiated Ar+ fluence, drastic changes on the GO surface properties have been also observed by means of wettability measurements in agreement with the suggested presence of DLCs. [ABSTRACT FROM AUTHOR]

The laser irradiation of TiH2 targets has been investigated to measure the proton energy transferred by hot non‐equilibrium plasmas in vacuum. The proton and titanium emission have been monitored by time‐of‐flight measurements to evaluate their maximum ion energy and dependence on the laser intensity. Backward and forward plasma have been generated in the range 1010–1016 W/cm2 intensity using ns and sub‐ns laser shots. Proton energy has been measured by tens eV up to about 4 MeV. The interest in proton beams generated by laser‐plasma is presented and discussed. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) have been produced by laser ablation in chloroform and then embedded in polylactic acid (PLA) thus realizing PLA/Au nanocomposite films. Two initial volumes of chloroform of about 5 and 4 mL have been used, thus obtaining two different PLA/Au nanocomposite films. The effects of the embedded AuNPs into PLA films have been studied using Attenuated Total Reflectance Fourier Transform Infrared (ATR–FTIR) spectroscopy and ultraviolet/visible (UV–Vis) absorption spectroscopy. In the ATR-FTIR spectra, as AuNPs are embedded in PLA and their concentration grows up, the PLA characteristic vibrational features maintain their positions in wavenumber, but their IR absorption increases. This result confirms the presence of AuNPs in PLA and suggests that no strong chemical interaction occurs between PLA and AuNPs and no new bonds are formed. Concerning the UV–Vis optical properties an increase in the PLA optical absorption in the visible region has been also observed when AuNPs are embedded. The AuNPs presence is attested by the appearance of localized surface plasmon resonance (LSPR) absorption peak between 500 and 600 nm that shifts at longer wavelengths and broadens as the AuNPs concentration increases. The PLA absorption edge has been determined and its position in wavelength increases with increasing AuNPs concentrations. This observed absorption edge red shift indicates a decrease in the PLA band gap probably due to the electronic levels introduced by the embedded gold nanoparticles. [ABSTRACT FROM AUTHOR]

Foils of graphene oxide (GO) prepared by micrometric graphene oxide platelets dispersed in water at low concentrations were physically investigated during their thermal reduction in a vacuum. The water, the carbon dioxide and the functional groups of oxygen, degassed during the thermal treatment, were monitored for the first time with a quadrupole mass spectrometer as a function of the foil temperature. Fourier transform infrared (FTIR) spectroscopy and energy dispersive X-rays (EDX) analyses were also presented to confirm the modality of reduction in vacuum. The thermal reduction process increases the C/O atomic ratio from the pristine value of about 2.0 to about 4.5 using a temperature of about 200°C. The reduced graphene oxide (rGO), depleted of water and some functional oxygen groups, shows a more compact structure with an increment of the density from the pristine value of about 1.36 g/cm3 to about 1.9 g/cm3, which determines a decreasing of the distance between the graphene layers. [ABSTRACT FROM AUTHOR]

At present graphene is the most exciting star in the materials science but graphene oxide, GO, that is its low-cost precursor attracts researchers from various fields because it is very easily produced at low cost. GO is an electrical insulator than can be transformed into graphene through the 'reduction' process. The oxygen functional groups it contains can be removed by various ways, also using lasers, ion beams and the intercalation process. The intensive research on graphene has allowed the rediscovery of various graphite-like layered materials with composition other than carbon, but properties are not yet fully known and with interesting possible applications. Among them, manganese thiophosphate, MnPS3, is a layered inorganic host matrix for making, through the intercalation-exfoliation-restacking technique, multi-functional hybrid thin films that can find application as optical switches, transparent coatings, in catalysis and photocatalysis, as lubricants, to create new multilayer structures, as dielectric substrates for graphene-based electronics and so on. If exfoliated at few layers, MnPS3 allows to realize good ultraviolet photodetectors with a gate tunable photoresponsivity and high photo gain. Recent progress in these graphene-like materials will be presented and discussed together with measurements based on the use of lasers, ion beams and intercalation emphasizing their potential applications. [ABSTRACT FROM AUTHOR]

Graphene-based materials have peculiar optical, electrical, mechanical and chemical properties, which make them useful for making thin films and thick sheets suitable for different needs. Matter physics, nuclear physics, microelectronics, biomedicine, engineering, agriculture and cultural heritage just represent some of the sectors in which these materials can be successfully used. The advancements allow us to go from a given graphene-based material to another transforming, for example, the insulator graphene oxide to electrically and thermally conductive reduced graphene oxide. Thanks to the interesting properties possessed by graphene-based materials, it is possible to realize gas sensors, dosimeters for ionizing radiation, light detectors, electronic devices, membranes for gases and desalination, biocompatible surfaces, medical protheses and thin coating films to preserve underlying layers. Different analysis techniques are presented to control the physical modifications of reduced graphene oxide (rGO) due to the different treatments for the pristine one. The paper reports the possibility to realize GO micro-dosimeters for ionizing radiations, sensors for air humidity and other gases, field effect transistors as the detector of visible and UV radiations, GO and rGO membranes realization for different gases, source ion strippers to enhance the charge state of different ions to be accelerated. Some of these aspects and possible applications will be presented and discussed with measurements carried out in our laboratories. [ABSTRACT FROM AUTHOR]

Measurements of the carbon dioxide (CO2) diffusion in graphene oxide (GO) and reduced graphene oxide (rGO) vs. temperature have been performed using uniform GO thin foils with15 μm thickness. Regarding rGO, its foils have been obtained by submitting GO at a temperature of 130 °C in vacuum for 30 min. The CO2 diffusion has been controlled by the gas pressure gradient applied to two faces of the thin foils versus the time and the temperature. The calculated CO2 coefficient diffusions have been compared with those relative to the nitrogen (N2) and argon (Ar) gases obtained in previous measurements. The deduced diffusion coefficients are different for the three investigated gases, but remain of the order of 10–3 cm2/s. At room temperature in GO the minimum value is obtained for nitrogen, while the highest one for Ar. Indeed, at 100 °C in rGO the minimum value is deduced for nitrogen and the maximum one for the carbon dioxide. The different diffusion coefficients can be attributed not only to the different size, shape and atomic mass of the investigated gases, but also to the inner lattice structure of the GO and rGO foils. GO contains water and oxygen functional groups which obstacle the diffusion process. rGO is poorer of oxygen functional groups and of water, partially enhancing the diffusion, but it has a high compactness and density which may reduce the total diffusivity. The obtained results, their correlation with the inner structure of the graphene sheets and the comparison between measurements and the literature data are presented and discussed. [ABSTRACT FROM AUTHOR]

The laser ablation is an established material processing for many applications in nanotechnology, materials science and biomedicine. The laser ablation can be carried out in vacuum, in air and in liquid. Laser ablation mechanisms and their products depend on laser fluence, wavelength, pulse duration, ablation environment as well as target composition, density, thickness, roughness. This contribution is addressed to laser ablation of solid targets with the aim of hot plasma generation and thin film deposition on substrates located in appropriate positions in vacuum and in air. In the first section is presented an example of forward and backward plasma accelerations using the sub-nanosecond laser at the PALS laboratory (Czech Republic) for pulsed laser deposition processing. In the second section is reported the use of a nanosecond laser coupled to a post-accelerating compact system employed at the INFN in Catania (Italy) to ablate germanium solid targets in vacuum and to deposit thin films on SiO2/Si substrates to modify their native features. The last section is focused on the use of the nanosecond laser at the Tandetron laboratory (Czech Republic) employed for pulsed laser deposition and laser-induced backward transfer processing in vacuum and in air. [ABSTRACT FROM AUTHOR]

Light trapping and luminescence have been observed in polydimethylsiloxane (PDMS) foils containing about 0.1–0.2 wt% gold nanoparticles (AuNPs). The so-prepared PDMSs have been physically characterized using SEM microscopy, UV–Vis, FTIR and Raman spectroscopies. The used AuNPs have been controlled by means of the surface plasmon resonance absorption spectra. In the AuNPs–PDMS foils, a luminescence peak at about 425 nm has been induced by an exciting light at 280 nm. The light injection with an optical fiber is trapped inside the polymer-containing NPs and illuminates all the polymer volume. The measurements of scattered light show an increment in the light intensity due to the presence of AuNPs and air bubbles inducing diffractions, reflections and Mie scattering. Further investigations have been conducted irradiating the PDMS with AuNPs in vacuum with 2.9 MeV proton beams producing luminescence in the blue region. The mechanisms of light trapping and luminescence and the possible applications of the prepared material are presented and discussed. [ABSTRACT FROM AUTHOR]

The pulsed laser cleaning (PLC) technique employing different laser wavelengths, with a ns pulse duration, is presented. Such a technique can be applied to the preservation of cultural heritage artworks on different materials, like metals, ceramics and glasses to clean the surfaces of debris accumulated over the years, to remove the oxidation layers, the dust, the organic materials and other unwanted layers, restoring their original composition and shape. PLC should be preceded by surface analyses to control the state of the surface before and during the cleaning process, which has to be carefully controlled, in order to stop the cleaning before to damage the underlying original surface. PLC examples, applied to metals, terracotta and glazy ceramics, are presented and discussed using IR, visible and UV pulsed laser irradiations at low intensity. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis of macro-porous polydimethylsiloxane (PDMS) sponges decorated with reduced graphene oxide and graphene is described using a top-down approach based on the sugar templating process. Among the multiple assets enjoyed by PDMS, its elasticity and porosity make possible the uniform dispersion of embedded graphene-based material into its structure. Where possible, the optical, surface and morphology properties of both porous PDMS composites and their not porous (bulk) counterparts have been studied. Scanning transmission ion microscopy (STIM), based on the reciprocity between the beam energy loss and the sample areal density, has been used to obtain the images of the sponge internal part. A detailed spatial resolution of the PDMS microstructure has been deduced by the areal density map. The homogeneous dispersion of the fillers was observed by scanning electron microscopy (SEM) and indirectly by light transmittance measures performed in several regions of the PDMS bulk. The reduced graphene oxide and graphene introduced into PDMS significantly improve its electrical conductivity. The porosity of the presented hybrid material holds a key role for good performances in microelectronics and biomedicine. [ABSTRACT FROM AUTHOR]

Proton acceleration can be induced by non‐equilibrium plasma developed by high‐intensity laser pulses, at 1016 W/cm2, irradiating different types of thin polyethylene targets. The process of proton acceleration and directive yield emission was investigated, optimizing the laser parameters, the irradiation conditions, and the target properties. The use of 600 J pulse energy, a laser focalization inducing self‐focusing effects and advanced targets with embedded nanoparticles and optimal thicknesses, has permitted to accelerate forward protons up to the energies of about 6 MeV and amount of the order of 1015 H+/pulse. High proton energy is obtained using thin foils enriched with gold nanoparticles, whereas high proton yield is obtained using targets with a thickness of about 10 μm. The plasma diagnostics using SiC semiconductor detectors in time‐of‐flight configuration was fundamental to monitor the optimal conditions to improve the plasma processes concerning the ion acceleration and the X‐ray and relativistic electron emission. [ABSTRACT FROM AUTHOR]

A laptop neutron source suited for the most demanding field or laboratory applications is presented. It is based on laser ablation of CD2 primary targets, plasma acceleration of the D+ ions, and their irradiation of secondary CD2 targets. The deuterium–deuterium (D‐D) fusion reaction is induced in the secondary target, according to the values of fusion cross‐section versus deuteron energy, which show a significant probability also at relatively low ion energies. The experiments were completed in the PALS laboratory, Prague, detecting monoenergetic neutrons at 2.45 MeV with an emission flux of about 109 neutrons per laser shot. Other experiments demonstrating the possibility to induce D‐D events were performed at IPPLM, Warsaw, and at INFN‐LNS, Catania, where the deuterons were accelerated at about 4 MeV and 50 keV, respectively. In the last case, a low laser intensity and a post‐ion acceleration system were employed. A special interaction chamber, under vacuum, is proposed to develop a new source of monochromatic neutrons or thermalized distribution of neutrons [ABSTRACT FROM AUTHOR]

The fs laser facility in Bordeaux, delivering an intensity of 1018 W/cm2 at normal incidence on thin foils, has been used to induce forward electron and ion acceleration in target‐normal‐sheath‐acceleration (TNSA) regime. Micrometric thin foils with different composition, thickness, and electron density, were prepared to promote the charge particle acceleration in the forward direction. The plasma electron and ion emission monitoring were performed on‐line using SiC semiconductor detectors in time‐of‐flight (TOF) configuration and gaf‐chromics films both covered by thin absorber filters. The experiment has permitted to accelerate electrons and protons. A special attention was placed to detect relativistic hot electrons escaping from the plasma and cold electrons returning to the target position. The electron energies of the order of 100 keV and of about 1 keV were detected as representative of hot and cold electrons, respectively. A high cold electron contribution was measured using low‐contrast fs laser, while it is less evident using high‐contrast fs lasers. The charge particle acceleration depends on the laser parameters, irradiation conditions, and target properties, as will be presented and discussed. [ABSTRACT FROM AUTHOR]

A compressible capacitive mechanical pressure sensor has been developed. Porous polydimethylsiloxane (p-PDMS) has been chosen as dielectric insulator because of its dielectric constant value. Gold nanoparticles have been embedded in p-PDMS to change the dielectric properties and to tune its elasticity. p-PDMS and its nanocomposite have been synthesized using the sugar leaching process. The p-PDMS physical characterization, with and without the gold nanoparticles, has been conducted to investigate its elastic response to compressive stresses as a function of both the polymer preparation thermal treatment and the gold nanoparticle concentration. A sensor operating in a low-pressure range between about 100 Pa and 10 kPa with a strain ranging between about 5% and 95% has been realized. Dielectric constant and electrical resistivity measurements have been performed using samples with a starting volume of the order of 1 cm3. The relationship between the dielectric constant, the electrical resistivity and the compressive stress/strain has been also deduced. The described sensor is flexible, biocompatible, water equivalent and can have applications in biomedicine (orthopedic, dentistry), engineering (stress–strain measurements, robotics), and microelectronics (microbalances, stress test on electronic devices). [ABSTRACT FROM AUTHOR]

Thick and thin films of Al targets were irradiated in vacuum with iodine laser at 1315 nm wavelength, 300 ps pulse duration at a maximum intensity of about 1016W/cm² by varying the pulse energy and focal position. The laser-generated plasma was monitored in forward and backward directions by using ion collectors, SiC detectors, Thomson parabola spectrometer, and X-ray streak camera. Ion emission shows maximum proton energy of about 4MeV in self-focusing conditions and a maximum Al ion energy of about 50MeV. An evaluation of the electric field driving ions in conditions of target normal sheath acceleration is given. [ABSTRACT FROM AUTHOR]

The INFN-CIMA project deals with the employment of graphene, graphene oxide (GO) and reduced graphene oxide (rGO) for applications in Nuclear Physics. In particular, the project aim is that to use the special properties of GO, which can be synthesized as a thin foil with 0.1–100 µm thickness, to realize thin films for solid ion strippers employed in ion accelerator sources with lifetime advantages with respect to the traditional graphite foils. rGO thin foils can be employment to develop laser-generated plasma and to accelerate protons and carbon ions in target-normal-sheath-acceleration (TNSA) regime. The GO can be also employed for the realization of special sensors of temperature, air relative humidity and gas. Moreover, it can be used to realize water-equivalent, biocompatible and low dimensional, dosimeters based on the lecture of the reduction level produced by the absorbed dose. Finally, graphene and rGO films can be applied to investigate the implemantation ofsmall radiation detectors. Many applications and experimental results will be presented and discussed. [ABSTRACT FROM AUTHOR]

Pulsed IR lasers were employed to irradiate high boiling elements, such as C, Mo, Ta, W and Re, in high vacuum. The ablation yield, given in terms of removed mass per pulse, was investigated using a ns laser at intensities of the order of 1010 W/cm2 and a sub-ns laser operating at about 1015 W/cm2. The produced plasma in high vacuum was studied by the time-of-flight measurements of emitted ions. The plasma-accelerated particles can be deposited and implanted on a near substrate to form a very adherent thin film useful for applications involving high temperatures and hard materials. [ABSTRACT FROM AUTHOR]

2.0 MeV proton beam accelerated at Tandetron is extracted in air through a thin film and allowed to scatter to irradiate the cell culture attached to the polymeric base of a biological flask. The irradiated cells were human medulloblastoma cell line Daoy treated with and without 5 nm sized spherical gold nanoparticles. Proton doses from 0.5 to 1.5 Gy have been employed to irradiate the cultures and to investigate the role of the radiotherapy performed with and without the use of the gold nanoparticles. Results indicated that cell survival is significantly reduced to about 50% when the nanoparticles at a concentration of about 6 × 1013 particles/ml are employed. [ABSTRACT FROM AUTHOR]

In this article, we report a study carried out to understand how changes in environment and temperature, in which the graphene oxide (GO) film reduction occurs, alter the electrical properties of the resulting films. In fact, it is possible to improve the GO reduction efficiency by choosing suitable environment and temperature. To this purpose, three different environments (high vacuum, air and nitrogen) and three dissimilar temperatures (177 °C, 300 °C and 600 °C) have been chosen, as suggested by differential scanning calorimetry (DSC) measurements. Among the investigated thermally reduced graphene oxide films, the ones treated at 600 °C in nitrogen have shown to possess higher electrical conductivity. Such an enhanced electrical conductivity can be attributed to reduction of oxygen functional groups and restoration of sp2 carbon network, as confirmed by Raman spectra. [ABSTRACT FROM AUTHOR]

The paper investigates the electrical properties of the junction between the graphene oxide (GO) and some metals (Cu and Au). A simple humidity sensor, based on the adsorption of water molecules on the GO/surface in a GO/Cu junction, is described. The GO was drop-casted as a thin film, 10 μm in thickness, on the metallic substrate. The junction open-circuit voltage and short-circuit current behaviours versus the humidity level can be explained on the base of the charge carrier drift. The room temperature response of the GO/Cu water vapour detector, in terms of relative humidity in air, is compared against a well-known commercial hygrometer. The proposed device does not require external polarization, and it is inexpensive and easy to use. [ABSTRACT FROM AUTHOR]

Solid targets have been irradiated in vacuum by an ns-laser pulse producing non-equilibrium plasma accelerating ions along the normal to the target surface. The ions emission can be focused by cylindrical permanent magnets in order to enhance the ion current. The electron traps formation along the main emission direction produces an electrical field driving further ion acceleration. Measurements using time-of-flight technique have been developed to quantize the focusing and accelerating effects induced by the applied magnetic field. Experimental measurements were compared with theoretical calculations obtained using COMSOL software, as it will be presented and discussed. [ABSTRACT FROM AUTHOR]

Thin foils of graphene oxide (GO) are irradiated by a fs titanium sapphire laser at an intensity of about 1019 W/cm2 in high vacuum. The produced plasma in the forward direction accelerates ions in a regime of target-normal-sheath-acceleration, thanks to the relativistic electron emission from the target surface and to their emission from the rear foil surface, generating a high electric field pulse with the positive target. The ion acceleration is measured mainly using SiC detectors in the time-of-flight configuration. Adding gold as nanoparticles or as a thin coverage film, the ion acceleration is enhanced as a result of a higher plasma electron density. The optimal acceleration is reached by varying the GO thickness, the Au nanoparticle concentration, the thin Au film thickness, and the irradiation conditions. Particularly important is the laser focal position with respect to the target surface, which is responsible for different acceleration values. In the used experimental conditions, a maximum proton energy of 2.6 MeV was obtained and the best modality to add Au atoms to the target is discussed. [ABSTRACT FROM AUTHOR]

Radiochromic films (RCF), also called GafChromic™ films, represent a performant material for accurate quantitative radiation dosimetry. Their compositions allow high dose sensitivity and fewer environmental dependence, giving a good feedback to the absorbed dose value and to the active media absorption, turning color upon being irradiated. The RCF take into account their reduced response near the Bragg peak due to a high linear energy transfer (LET). HD-810 GafChromic™ films are tissue-equivalent, have easy optical readings and can be employed for ion dosimetry in radio diagnostic and therapy and for industrial applications. Such dosimeters were employed at Tandetron-Nuclear Physics Institute (Řež, Czech Republic) to study the responses of helium, proton and carbon beams, commonly employed in radiotherapy and microelectronics. The sensitivity of the detector is low enough to measure multiple-beam exposures. The induced effects by the ions in the energy range of 600 keV to 2.0 MeV were investigated in terms of optical absorbance, measured in the irradiated active region of the polymer. The employed ion dose range was between 40 Gy and 2.5 kGy. The experimental results show that the absorbance increases with the irradiation time (i.e. with the absorbed dose). The absorbance induced in the radio chromic film was measured at 673 nm, at which is observed the highest sensitivity of the films. Such data, together with the dose linearity and the dependence on the ion stopping power will be presented and discussed. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) is a two-dimensional material, which is attracting increasing attention due to its special properties. It can be obtained by laser or ion beam irradiations of pristine graphene oxide (GO). It shows high mechanical resistance, considerable electric and thermal conductivity. All these rGO characteristics together with the high number of molecular species that can be embedded between its layers, make graphene oxide a potential material for electronic sensors or efficient support on which conductive strips, condensers, and micrometric electronic devices can be designed. In particular, as it is described in this paper, it is possible to carry out high spatial resolution lithography in GO by using a focused laser or micro ion beam in order to design macro, micro, and submicron geometrical structures. The use of the reduced graphene oxide for the laser and ion beam fabrication of electrical resistances and capacitances is presented. [ABSTRACT FROM AUTHOR]

Two well-established electrical insulators, graphene oxide and poly(methylmethacrylate) (PMMA) have been selectively exposed to controlled energy and fluence of ions. Ion micro beam has been proposed for processing of both graphene-based material and polymeric foils for tailoring of their properties. In a single step, the mask-less production of pattern on graphene-oxide and poly(methylmethacrylate) was realized at the Tandetron Laboratory of the Nuclear Physics Institute (Czech Republic) using a stream of 2.2 MeV alpha particles. Elements of a circuit were written on GO and poly(methylmethacrylate) in a controlled way using a software written in LabVIEW code. The induced deoxygenation, and dehydrogenation change the compositional, structural and electrical properties in the exposed samples. The accuracy of the method has been investigated by Rutherford backscattering spectrometry, elastic recoil detection analysis, Raman microscopy and the electrical standard two points method. [ABSTRACT FROM AUTHOR]

A new type of ion dosimeter based on graphene oxide (GO) foils is presented and discussed. GO is biocompatible, stable, tissue equivalent and has special chemical and physical properties. The ion irradiation reduces the material thanks to the breaking of oxygen functional groups bonded to the carbon matrix and to the consequent their desorption. The reduction effect increases the carbon-to-oxygen atomic ratio and transforms the pristine insulator GO into the semiconductive reduced GO (rGO). The reduction increases with the ion dose making the material more electrically conductive, decreasing its band gap and making it denser. At high doses of 2 MeV helium beam irradiation, the electrical conductivity increases linearly with the ion fluence for values within 1011 and 5 × 1014 ions/cm2, corresponding to absorbed doses of 25.9 kGy and 129.55 MGy, respectively. The results indicate that this material reduction is controllable through the desorption of oxygen groups and absorbed hydrogen, by the increment of the electrical conductivity and by the surface roughness, all these parameters depending on the absorbed dose by the material, which can be a good candidate to realise small ion dosimeters, especially to be used in the small-field dosimetry. [ABSTRACT FROM AUTHOR]

Gold nanoparticles were prepared by laser ablation in water and then characterized through physical analyses, in the perspective to be employed for different applications in the fields of Physics and Bio-Medicine. Different parameters have to be taken into account, such as the surface wetting ability, the possibility to improve the contrast image in microscopic and macroscopic systems and the enhancement of deposited dose by radiotherapy and thermal therapy treatments. The presence of a high-Z element, in fact, allows to modify the chemical and physical properties of materials and to release energy from ionizing radiation or from light absorption in the matter in which Au nanoparticles are embedded. These factors enhance the energy released to diseased tissues increasing the radiation effects in cells, for instance, the DNA of cancer cells can be destroyed with more efficiency due to the higher released dose inside the cell. [ABSTRACT FROM AUTHOR]

This work introduces an innovative new method to transport gold nanoparticles (Au-NPs) toward specific organs using as transporter the M13 filamentous phage. The aim is to improve the radiotherapy efficiency by injecting gold nanoparticles in the tumor tissues in order to increase the effective atomic number and, consequently, to produce higher locally deposited doses. The biocompatible Au-NPs can be bonded to the phage surface for their transport in the biological fluids and tissues. M13 phages can be prepared to arrive in specific tissues and organs depending on their biochemical preparation and functionalization. Evidence about the real attachment of spherical Au-NPs, 10 nm in diameter, to the M13 phages is obtained using different microscopies. Other analyses have been also performed to evaluate the number of gold nanoparticles that can be transported by M13 phages inside the organism. Our results on the study of the spherical Au-NP size distribution, deduced by AFM, EFM, and TEM analyses, have indicated that in average, 2 couples of Au-NPs are attached to each phage. Moreover, the size of the NPs ranges between 10 and 30 nm, demonstrating a little aggregation of the nanoparticles, which remain usefully sized to be vehicled with the blood flux towards specific organs. [ABSTRACT FROM AUTHOR]

Gafchromic HD-V2 films are employed to study the response to light ions useful in radiotherapy, such as protons, helium and carbon beams. The effects induced by the ions at an energy within about 300 keV and 16 MeV were investigated in terms of optical absorbance measurements in the irradiated active region of the film. The employed ion doses range between 0.4 Gy and 12 kGy. The results show that the net optical density increases almost exponentially with the absorbed dose and that it becomes saturated after prolonged dose higher than 1 kGy. The optical density produced in the film was measured by light transmission measurements at 700 nm wavelength, at which is observed the highest gafchromic sensitivity. Calibration curves of optical density versus exposure dose and type of ion are given. The dependence on the ion stopping power was presented and discussed. [ABSTRACT FROM AUTHOR]

Particle in cell simulation was applied to fit the measurements of protons and ions acceleration obtained using an fs laser pulse irradiating a thin foil in target-normal-sheath-acceleration regime. The simulation code calculates the maximum electrical field generated in the rear side of the target driving the forward ions acceleration. The electron density versus time and space, and the plasma temperatures are evaluated using a medium contrast laser at an intensity of about 1019 Wcm−2. Proton acceleration above 10 MeV was experimentally measured using SiC detectors connected in time-of-flight configuration. A comparison between theoretical aspects and experimental data is reported and discussed. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide (rGO) films can be employed as ion strippers in an accelerator. They show some advantages with respect to the graphite foils, due to their high thermal and electrical conductivity, low density, high mechanical resistance and high stability. Thin graphene oxide (GO) films with a sub-micron thickness have been synthesized and transformed into reduced GO (rGO) by ion beam irradiations. Physical characterizations of the pristine and ion irradiated GO films have been performed. Measurements of stripping efficiency have been carried out by using helium, lithium, carbon and oxygen ion beams. The rGO stripper films demonstrate a significantly high charge production, comparable to that of the graphite films but with the advantage of a longer lifetime. [ABSTRACT FROM AUTHOR]

Multi-MeV beams of light ions have been produced using the 300 picosecond, kJ-class iodine laser, operating at the Prague Asterix Laser System facility in Prague. Real-time ion diagnostics have been performed by the use of various time-of-flight (TOF) detectors: ion collectors (ICs) with and without absorber thin films, new prototypes of single-crystal diamond and silicon carbide detectors, and an electrostatic ion mass spectrometer (IEA). In order to suppress the long photopeak induced by soft X-rays and to avoid the overlap with the signal from ultrafast particles, the ICs have been shielded with Al foil filters. The application of large-bandgap semiconductor detectors (>3 eV) ensured cutting of the plasma-emitted visible and soft-UV radiation and enhancing the sensitivity to the very fast proton/ion beams. Employing the IEA spectrometer, various ion species and charge states in the expanding laser-plasma have been determined. Processing of the experimental data based on the TOF technique, including estimation of the plasma fast proton maximum and peak energy, ion beam currents and total charge, total number of fast protons, as well as deconvolution processes, ion stopping power, and ion/photon transmission calculations for the different metallic filters used, are reported. [ABSTRACT FROM AUTHOR]

The time and space resolved characterization of laser-generated pulsed plasmas is useful not only for the comprehension of basic phenomena involved in the plasma generation and following supersonic expansion, but it also permits to control the nonequilibrium process that is useful for many applications (e.g., ion implantation). The “on-line” characterization can be performed by means of Langmuir probes, ion collectors, and ion energy analyzers, in order to measure the plasma temperatures and densities of atoms, ions, and electrons. The investigated plasmas were generated by means of laser pulses with intensity of the order of 109 W/cm2. The contemporary characterization of the electron (through the Langmuir probe) and ion energy distribution functions, EEDF and IEDF, respectively, permits to correlate the ion properties, like charge states and temperatures, with the electron properties, like the shape of the EEDF at different times and distances from the ablated target surface. [ABSTRACT FROM AUTHOR]

A single-crystal silicon carbide (SiC) detector was used for measurements of soft x rays, electrons, and ion emission from laser-generated plasma obtained with the use of the Prague Asterix Laser System (PALS) at intensities of the order of 1016 W/cm2 and pulse duration of 300 ps. Measurements were performed by varying the laser intensity and the nature of the irradiated target. The spectra obtained by using the SiC detector show not only the photopeak due to UV and soft x-ray detection, but also various peaks due to the detection of energetic charged particles. Time-of-flight technique was employed to determine the ion kinetic energy of particles emitted from the plasma and to perform a comparison between SiC and traditional ion collectors. The detector was also employed by inserting absorber films of different thickness in front of the SiC surface in order to determine, as a first approximation, the mean energy of the soft x-ray emission from the plasma. [ABSTRACT FROM AUTHOR]

A monocrystalline diamond detector was used for measurements of soft x-ray and ion emission from laser plasma obtained with the use of the PALS Asterix laser at intensities on the order of 1016 W/cm2 and pulse duration of 300 ps. Measurements were performed by varying the laser intensity and the focal position of the laser beam with respect to the target position. The spectra were obtained with the use of a diamond detector, which was without a filter, and showed not only the photopeak due to UV and soft x rays but also the ions emitted from the plasma. The detector was employed with absorbers of different thicknesses to determine, as a first approximation, the energy distribution of soft x-ray emission from the plasma. The time-of-flight technique was employed to determine the ion kinetic energies. [ABSTRACT FROM AUTHOR]

A study of visible laser ablation of tantalum in vacuum by using 3 ns Nd:YAG laser radiation at high pulse energy is reported. Nanosecond pulsed ablation, at an intensity on the order of 109 W/cm2, produces high nonisotropic emission of neutrals and ionic species. Mass quadrupole spectrometry, coupled to electrostatic ion deflection, allows estimation of the energy distributions of the emitted species within the plume as a function of the incident laser energy. Neutrals show typical Boltzmann distributions while ions show Coulomb-Boltzmann-shifted distributions depending on their charge state. Surface profiles of the craters and microscopy investigations permitted to study the ablation threshold, ablation yields, and deposition rates of thin films on silicon substrates. The multicomponent structure of the plume emission is rationalized in terms of charge state, ion and neutral equivalent temperatures, and plasma density. A special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at the nonequilibrium plasma conditions. The angular distributions of the neutral and ion species are also presented and discussed. [ABSTRACT FROM AUTHOR]

High energy laser, 400 ps pulse duration, irradiating heavy targets in vacuum produce intense plasma and generate emission of various energetic ion groups. The ion intensity is high along the normal to the irradiated target surface and high charge state and high velocity ions are produced. The characteristics of the ion streams were investigated by using an electrostatic ion energy analyzer and different ion collectors were placed at various angles with respect to the target normal. The ion energy distribution as a function of the ion charge state was measured and the comparison of the properties of different ion groups generated by laser beams at two different energies was carried out. Measurements point out that five ion groups or more can be generated by the laser interaction with the preformed plasma, with different “equivalent ion temperatures.” Slow, thermal, fast, and very fast ions follow a Boltzmann-like distribution; the equivalent temperatures of different ion groups were estimated to reach values up to about 80 keV. [ABSTRACT FROM AUTHOR]

The experiment concerning the ECLISSE method (ECR ion source coupled to a laser ion source for charge state enhancement) has been carried out by coupling a laser ion source (LIS) to the superconducting electron cyclotron resonance source (SERSE) electron cyclotron resonance (ECR) ion source with the goal to obtain intense beams of highly charged ions (cw or pulsed mode) from metal samples, especially from refractory elements. The coupling efficiency of the ion beam produced by the LIS with the ECR plasma was remarkable and the measured beam intensities were quite high. The maximum charge states, obtained with a good reproducibility, were 38+ for Ta and 41+ for Au. The highest current was obtained for 25+ and 28+ for Ta and Au ions, respectively, and it was in both cases of the order of some tens of microampere, i.e., higher than the current obtained from SERSE with other methods (i.e., evaporation and sputtering). The ion beam stability and reproducibility were both acceptable. The possibility to get a further enhancement of the available charge states was limited by charge exchange processes connected with the target ablation. The main features of the LNS facility based on a Nd:YAG (yag, yttrium aluminum garnet) laser (0.9 J/9 ns, laser power densities <5×1010 W/cm2) and on the SERSE superconducting ECRIS working in single frequency mode (18 GHz) will be shown in the following. The analysis of the results and the way to get rid of the existing limits will be also presented and discussed. [ABSTRACT FROM AUTHOR]

A Q-switched Nd:YAG (yttrium aluminum garnet) laser (1064 nm wavelength) with a 9 ns pulse width, 1-900 mJ pulse energy, and 0.5 mm² target spot, is employed to irradiate tantalum targets in vacuum. The irradiation produces a strong etching of the metal and forms a plasma in front of the target. The plasma contains neutrals and ions with a high charge state and a wide energy distribution. Time-of-flight measurements are presented for the ionic production. A cylindrical electrostatic ion analyzer permits to measure the yield and the charge state of the emitted ions and to extrapolate the ion energy distribution as a function of the laser fluence in the range 10-100 J/cm². The measurements indicate that at high laser fluence the tantalum charge state may reach 8+ and the maximum ion energy about 6 keV. The ion energy distribution is presented as a function of the charge state. It follows approximately a "shifted Maxwellian distribution." A better theoretical approach has been further developed considering the Coulomb interactions occurring inside the plasma, which produce ion acceleration at velocities comparable with thermal ones, according to the so-called "shifted Maxwellian-Coulombian distribution. [ABSTRACT FROM AUTHOR]

The laser ablation of boron-nitride (BN) ceramic was employed for the preparation of thin films in high vacuum and nanoparticles and nanocrystals generated in water. The obtained plasma was investigated using ion detectors to determine the ion velocity, the energy per charge state and the plasma temperature and describing the acceleration mechanism. The kinetics of laser ablation in water and the comparison of different ablation rates in the vacuum and in water, and the possible applications of the BN thin film and nanoparticles are presented and discussed. [ABSTRACT FROM AUTHOR]