Fabio Belloni

• Ph.D. in Physics
• Plasma Physics, Nuclear Physics, Applied Physics, Materials Science at European Commission, Directorate-General for Research & Innovation

We have revisited recent results on the ideal ignition of H ¹¹ B fuel, in the light of the latest available reactivity, an alternative self-consistent calculation of the electron temperature, an increased extent of the suprathermal effects and the impact of plasma density. At high density, we find that the ideal ignition temperature is appreciably...

The nuclear fusion channel of the p- ¹¹ B reaction producing α particles with multi-MeV kinetic energies was induced by a sub-nanosecond laser pulse focused onto 10 μm thick boron-doped thin targets at intensities of ∼ 10 ¹⁶ W/cm ² . A full characterization in terms of α particle flux and angular distribution was performed thanks to the simultaneou...

Proton-boron fusion is experiencing a renewed interest as a possible energy source. The reaction is aneutronic and does not involve radioactive species. It has recently been induced by means of high-power lasers. Ignition of H- ¹¹ B fuel, however, remains challenging because of the low reactivity and high radiative losses of the plasma at temperatu...

The topic of proton-boron fusion has recently attracted considerable interest in the scientific community, both for its future perspectives for energy production and for nearer-term possibilities to realize high-brightness α-particle sources. Very interesting experimental results have been obtained, in particular in laser-driven experiments but als...

HB11 Energy’s mission is to realize large-scale electricity generation from the fusion of hydrogen with boron-11 (the HB11, or “proton-boron”, reaction) without the environmental problems normally associated with nuclear energy. A non-thermal approach is taken in the initiation of the reaction using high-peak-power lasers, which was the pursuit of...

Nuclear fusion between protons and boron-11 nuclei has undergone a revival of interest thanks to the rapid progress in pulsed laser technology. Potential applications of such reaction range from controlled nuclear fusion to radiobiology and cancer therapy. A laser-driven fusion approach consists in the interaction of high-power, high-intensity puls...

Proton-boron fusion would offer considerable advantages for the purpose of energy production as the reaction is aneutronic and does not involve radioactive species. Its exploitation, however, appears to be particularly challenging due to the low reactivity of the H-11B fuel at temperatures up to 100 keV. Fusion chain-reaction concepts have been pro...

The ¹¹B(p,3α) fusion reaction is particularly attractive for energy production purposes because of its aneutronic character and the absence of radioactive species among reactants and products. Its exploitation in the thermonuclear regime, however, appears to be prohibitive due to the low reactivity of the H–¹¹B fuel at temperatures up to 100 keV. A...

The $^{11}$B$(p,\alpha)2\alpha$ fusion reaction is particularly attractive for energy production purposes because of its aneutronic character and the absence of radioactive species among reactants and products. Its exploitation in the thermonuclear regime, however, appears to be prohibitive due to the low reactivity of the $^{11}$B fuel at temperat...

The nuclear reaction known as proton-boron fusion has been triggered by a subnanosecond laser system focused onto a thick boron nitride target at modest laser intensity (∼10 16 W/cm 2), resulting in a record yield of generated α particles. The estimated value of α particles emitted per laser pulse is around 10 11 , thus orders of magnitude higher t...

The possibility of triggering an avalanche reaction in laser-driven p-¹¹B fusion by the effect of collisional energy transfer from α particles to protons has recently been debated, especially in connection to the high yield of α particles (4 × 10⁸ per laser shot) achieved on engineered targets at the Prague Asterix Laser System (PALS), with a pulse...

This paper suggests that a change in the lifetime of the α-decay process in Am241 may be detected at high pressures achievable in the laboratory, essentially, due to the extraordinary high compressibility of Am at the megabar range. The Thomas-Fermi model was used to calculate the effect of high pressure on the atomic electron density and the varia...

The influence of the electron environment on the alpha decay is elucidated. Within the frame of a simple model based on the generalized Thomas-Fermi theory of the atom, it is shown that the increase of the electron density around the parent nucleus drives a mechanism which shortens the lifetime. Numerical results are provided for 144Nd, 154Yb and 2...

Active interrogation of special nuclear materials (SNM) represents the most promising detection technique in combating their illicit trafficking and diverted use. Among the many interrogation approaches under investigation, the one based on photoinduced fission relies on large prompt and delayed radiation signatures. Pulsed induction (tens of ns) o...

In light of recent speculations on a potentially increased speed of the radioactive decay of α-emitters embedded in a metallic matrix at very low temperature, four high-purity Cu disks deep-implanted with Bi209 were prepared. The disks were irradiated in a high-flux reactor to transmute the Bi209 into Po210. After the irradiation, the Po210 activit...

Adsorption of Sr on multi-walled carbon nanotubes (MWCNTs) was investigated to explore their possible use as an efficient adsorbent for nuclear waste streams. MWCNTs were purified and oxidized with HNO3 prior to testing adsorption. Oxidized MWCNTs were then employed in batch experiments as sorbent of Sr from aqueous solutions. The Box–Behnken exper...

To understand the mechanism of fuel oxidation, in the event of exposure of spent nuclear fuel to groundwater in a final repository, the key parameters are the diffusion coefficients for oxygen and water in UO2. In the temperature range relevant for geological disposal (20–100 °C), we conducted static corrosion experiments, for 3–6 months, with 18O-...

The last calls of the EU 7th Framework Programme for research have been already published. About EUR 195 million have been invested in research and demonstration projects on photovoltaics with the first five calls of the Programme. The actions to transform the photovoltaic market are carried out with the second Intelligent Energy Europe Programme....

Most of the surface explosions in nuclear tests have released radioactivity to the environment in the form of bulk glassy materials originating from the melting of sandy soil in the neighbourhood of ground zero. In view of clarifying issues concerning the mechanism of formation and the radiological impact of these materials, we investigated incorpo...

This work is devoted to characterizing the plasma produced by nanosecond laser ablation. The expanding plasma was generated by the interaction of a home made XeCl excimer laser with a Cu target. The time-of-flight method was utilized as diagnostic tool of the plasma charged particles. By this method, in fact, we were able to measure the ion and ele...

Oxygen and water species (e.g., OH−, H2O) diffusion in polycrystalline UO2 are key parameters to investigate in order to predict spent fuel behaviour in a final repository in the event of exposure to groundwater. In this work, 18O tracer diffusion is evaluated by means of secondary ion mass spectrometry on a UO2 pellet exposed to 18O-labelled water...

Following containment failure in the scenario of geological disposal of spent nuclear fuel, the penetration rate of groundwater into the UO2 matrix could cause a rapid increase of the fraction of inventory becoming available for prompt dissolution. In this respect, oxygen and water diffusion mechanisms are key issues to investigate. In this work, s...

of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

XANES has been recently used for the determination of oxidation states of actinides in environmental samples. To obtain reliable results, however, a sufficiently long counting time at every probing energy and a large number of experimental points per XANES spectrum are required, due to the complex mathematical model used to fit the measured spectru...

The development of a complete, standard analytical procedure for a quantitative use of secondary ion mass spectrometry to map the distribution in animal tissues of exogenous isotopes presents difficulties inherently related to sample preparation and preservation, as well as to the specific application being considered. We have tested in two very di...

Carbon nanotubes possess physicochemical properties that make them an attractive possibility for nuclear waste management, though much investigation needs to be done.

A porous silicon based hydrogen filter has been designed in STMicroelectronics R&D centers with the purpose to increase hydrogen permeation in systems where high purity gaseous hydrogen is required. The use of Pd alloy membranes is quite well established when hydrogen separation from other gases is needed, as, for example, in hydrogen generation sy...

The problem of correlation between the temperature of the target surface and the mass-spectrometer signal in laser-vaporization mass spectrometry has been analyzed theoretically. An approach based on statistical mechanics has been applied in order to describe the transient vaporization into vacuum of molecules effused from the area of the target su...

Effects of laser irradiation of Carbon nanotubes (CNTs) were investigated. Samples were laser-processed in different source conditions: pulsed laser beam of 248 nm, 532 nm and 1064 nm; pulse energy range from 100 mJ up to 500 mJ and shots number from 50 to 1800. Surface morphological changes and grain size distribution variations induced by the las...

The laser cleaning of corroded metals is not easily controllable because it is strongly influenced by a great number of factors, such as the laser parameters (wavelength, pulse width, laser fluence, shot number, etc.) and the material properties (chemical composition, optical characteristics, etc.). In particular, this is a cru cial problem in lase...

The physical modifications induced by ion implantation of ultra-high-molecular-weight-polyethylene (UHMWPE) by using a laser ion source (LIS) emitting multi-energy ion streams are investigated. A UV pulsed laser was employed to produce the plasma of the implanting material. The surface mechanical properties of UHMWPE depend on the implanted dose, w...

We report on the different behavior of electron and ion currents recorded by a Faraday cup in a plasma bunch generated via laser ablation. An excimer laser was employed to irradiate a Ge target. The current signals were recorded equipping the Faraday cup collector by a set of diaphragms. We found that the electron time-of-flight spectra were fairly...

A novel technique for ion implantation of electronics materials by means of a laser ion source emitting multi-energetic ion streams was investigated. A UV pulsed laser beam, at intensities of the order of 108 W/cm2, was employed to produce plasma in a vacuum from a Ge target. The apparatus utilized was very versatile and able to contain an expansio...

A UV pulsed lasers was employed to produce C and Ti ions of different charge with current densities of the order of 10 mA/cm2. A post ion acceleration, up to 30 kV, was employed to increase the ion energy and to implant polyethylene biocompatible surfaces up to a depth of about 200 nm. Preliminary results about surface properties indicate that impl...

Laser-induced plasmas are transient systems rapidly aging in few nanoseconds of evolution. Time-of-flight spectrometry allowed studying initial plasma characteristics based on frozen translational degrees of freedom, hence overcoming intrinsic limitations of optical spectroscopy. Experimental ion velocity distributions were reconstructed as develop...

We report temperature and drift velocity measurements on the ion component of a plasma produced by the interaction of a UV laser beam with a Cu solid target. A XeCl excimer laser (308 nm wavelength, 20 ns pulse duration, 70 mJ pulse energy) was used, achieving a power density on the target of about 0.3 GW/cm2 after beam focusing. The diagnostics wa...

A suitable plane transmission line was developed and its behaviour analysed at 900 MHz radiofrequency fields to study DNA mutability and the repair of micro-organisms. In this work, utilizing such a device, we investigated the behaviour of DNA mutability and repair of Escherichia coli strains. The transmission line was very simple and versatile in...

recA1, recA13 and recA56 are considered null alleles of the Escherichia coli recA gene because they were shown to have essentially no activity in vivo. In this study, we used strains harboring the recA null alleles and their recA-proficient congenic counterpart to assess the lethal and the mutagenic effects elicited by near-UV(308 nm) coherent radi...

An experimental study of the laser ablation produced plasma evolution is necessary for its deeper understanding, since plasma expansion has both spatially and temporally varying characteristics. We irradiated a Cu target with a KrF laser beam. A small Faraday cup array and an axial Faraday cup were used as diagnostic systems, in order to study the...

In this work the mutagenic effect on Escherichia coli strains induced by UV radiation emitted by a XeCl laser (lambda = 308 nm) has been analysed as a function of the exposure dose and compared with the effect induced by 254 nm radiation emitted by a conventional germicidal lamp. E. coli strains, wild-type (recA+) and mutant (recA1, defective in DN...

This work reports on a novel sterilization technique for bacteria which may be involved in deterioration of cellulose-based antiquities (paper, textile and wood). The bacterium we processed, a Nonomuraea sp. strain, was a mycelial microorganism belonging to the Actinomycetes group. This group includes many microorganisms that are able to attack cel...

We report here on the expansion dynamics of a non-equilibrium plasma produced by an excimer laser interaction with a Cu solid target. Its characteristics were investigated in the fast and slow time regime by two Faraday cups of different diameter. The larger cup had an 8 cm diameter collector and was fixed along a drift tube at a distance of 20 cm...

Knowledge of the relative abundance and the energy distributions of various ion species produced in laser ablation plasma is essential both in the fundamental physics ground, to understand the thermalization and expansion dynamics of the plasma plume, and in the applied physics ground, to obtain an efficient and versatile ion source. We present mea...

This study is devoted to characterizing a free expansion laser plasma produced by an excimer laser with respect to recombination phenomena. The plasma was ejected from a Cu target after the laser pulse. The diagnostic system was a Faraday cup located at different distances from the target in order to collect the ions carried by the plasma. Ion reco...

Two novel circuits used to amplify electric pulses by the coupling of transmission lines of different characteristic impedance are described. The circuits are intended for doubling voltage pulses and for doubling current pulses. The former is composed by a R0 transmission line closed on a set of two 2R0 storage lines connected in parallel, while th...

The precise characterization of plasmas generated by laser irradiation is needed for the development of ion sources. As the characteristic parameters of the expanding plasma vary with both the distance and the time, an experimental study of their evolution is appropriate for a deeper knowledge of the plasma. The purpose of this work is to study the...

In this work the experimental and simulation results of photoemission studies for photoelectrons are presented. The cathode used was a Zn disc having a work function of 4.33 eV. Two different excimer lasers were employed as energy source to apply the photoelectron process: XeCl (308 nm, 10 ns) and KrF (248nm, 23ns). Experimental parameters were the...

In this work we report the description of two novel circuits used to amplify electric pulses by the coupling of transmission lines of different characteristic impedance. One circuit is employed for doubling voltage pulses and one for doubling current pulses. The former is composed by a R0 transmission line closed on a set of two 2R0 storage lines c...

We report a new implantation technique via laser ion source. By applying a high voltage on the accelerating gap, this compact device was able to accelerate towards a substrate ions from ablation plasma. The occurrence of arcs during the extraction phase was a major problem to overcome. A pulsed KrF laser was utilized to produce plasma by ablation f...

The laser ablation-induced plasma was used as a composition-controlled source for ion implantation in Si crystals. Then, laser ablation in combination with inductively coupled plasma mass spectrometry was used for the elemental depth profiling of the implanted samples. Monte Carlo simulations permitted us to conclude that a depth resolution of tens...

The high-power iodine laser of the Prague Asterix Laser System (PALS), emitting radiation at 438 nm wavelength, 400 ps pulse duration and about 250 J maximum pulse energy, was employed to irradiate in vacuum a germanium target. The amount, the energy and the charge state of the ions emitted from the laser-produced plasma are analyzed by time-of-fli...

In this paper, we report investigations of the electron emission from pure Zn cathodes irradiated by UV laser pulses of 23 ns (full-width at half-maximum) at a wavelength of 248 nm (5 eV). The metal cathodes were tested in a vacuum photodiode chamber at 10−5 Pa. They were irradiated at normal incidence and the anode–cathode distance was set at 3 mm...

In this work, wave formation in laser-produced plasma is investigated by an analysis of time-of-flight signal of the electron pulse. Electrons are extracted from a non-equilibrium plasma, generated by pulsed laser ablation on a solid Ge target. The process is represented by ion-acoustic waves, which are generated from an external perturbation, give...

The precise characterization of plasmas generated by laser irradiation is needed for the development of ion sources. As the characteristic parameters of the expanding plasma vary with both the distance and the time, an experimental study of their evolution is appropriate for a deeper knowledge of the plasma. The purpose of this work is to study the...

We report on the ion implantation by a new laser ion source (LIS). It is able to accelerate plasma ions towards substrates by means of a polarized accelerating gap. A pulsed excimer laser, KrF, was utilized in producing plasma by target ablation. A laser pulse energy of 70mJ was focused onto different solid targets by a 15cm focal length lens, obta...

Experimental results concerning the extraction of Cu ions from laser-produced plasma are reported in this work. An XeCl excimer laser was used, providing a power density on the target surface of about 3.5×108W/cm2. Laser wavelength and pulse duration were 308nm and 20ns, respectively. The experimental apparatus consisted substantially of a plasma g...

The ion emission from a Cu-plasma produced by a 308 nm excimer laser is analysed by time-of-flight spectroscopy and by deconvolution of measured ion currents. The ion current signals recorded by an ion collector outside the critical zone, where the charge-states of ions of the expanding plasma are frozen, have been deconvoluted by the use of the Ke...

In this work we report the preliminary experimental results on the selective ablation of sulphur in ancient stones. The sulphur concentration was reduced after laser action. For this goal an excimer laser operating at 308 nm wavelength and time duration of 20 ns was used. In order to estimate the sulphur concentration before and after laser cleanin...

Utilizing a suitable irradiating transmission line chamber, the effects of 900 MHz radio frequency fields on DNA mutability and repair in Escherichia coli strains were investigated. The transmission line was very versatile and able to easily apply different field values. In this experiment the maximum electric and magnetic fields were 66 V/m and 26...

We report here the results about the sulphur concentration in ancient stones and its removal after the application of UV laser action. A portable apparatus for energy-dispersive X-ray fluorescence (EDXRF) was utilised to measure the sulphur concentration before and after laser cleansing. After laser application the sulphur concentration decrased to...

In this work an ion acceleration system based on a laser ion source was studied. It was able to generate ion beams utilizing as a source a laser plasma produced by a XeCl laser from a copper target. The focused laser beam provided a power density on the target surface of about 3.5x108 W/cm2. Laser wavelength and pulse duration were 308 nm and 20 ns...

The emission of multiply charged Cuq+ ions from a plasma produced by 308 nm excimer laser is analyzed with respect to the distance from the irradiated target. The critical zone, outside which the charge states of ions of the expanding plasma are frozen, was determined to be approximately 20 cm from the target. This value was estimated using a charg...

In this paper we illustrate the theoretical analysis, design, computer simulation, experimental realization and results of a circuit able to compress a rectangular pulse and to increase its intensity. Utilizing a pulse forming line, l long, and a halved storage line, l/2 long, both connected on the same load resistor by means of fast switches, a ti...

In this work the mutagenic effect on Escherichia coli strains of UV radiation emitted by a XeCI laser (lambda=308 nm, tau=20 ns, 100 mJ pulse energy) has been analyzed as a function of the exposure dose and compared with the effect induced by 254 nm radiation emitted by a conventional germicidal lamp. Mutations can involve any genome site and there...

The experimental results of particle acceleration by plasma generated using a XeCl laser are described. The laser ion source developed is able to accelerate specific particles and to overcome the plasma effects which occur specially during the application of the accelerating voltage. In order to successfully execute this experiment, plasma expansio...

We report on the results concerning the characteristics and the behavior of expanding plasma generated by a Laser Ion Source (LIS). The LIS technique is an efficient means in producing of multi-charged ions utilizing pulsed laser beams. In order to extract Cu ions, in this experiment an XeCl excimer UV laser was employed, providing a power den...

In this work the study of a laser ion source (LIS) by focusing an UV excimer laser beam onto a solid copper target is presented. The laser energy was 70 mJ concentrated by a convergent focal lens in a small spot. The efficient spot was about 1 mm2 determined by scanning the laser beam on lens focal plane and taking in account the threshold ablation...

In this work we report results concerning the characteristics of an expanding plasma used as Laser Ion Source (LIS). Plasma characteristics influence the deposition quality of pulsed laser deposition (PLD) films and the ion injection efficiency. The LIS technique is an efficient way to produce multi-charged ions by utilising pulsed laser beams. In...

The main characteristics of a laser-plasma are its temperature and drift velocity. In time-of-flight (TOF) measurements, they are determined by fitting the plasma signal by means of a function derived by the so-called "shifted" Maxwell-Boltzmann distribution for the plasma particle velocity. With this technique, in the present work the variation of...

In this work the experimental results of a nonequilibrium laser-plasma induced by an ultraviolet 308 nm excimer laser are reported. All measurements were performed fixing the laser energy at 70 mJ. It was concentrated on a 0.0099 cm 2 spot by a convergent focal lens of 15 cm focal length. The utilized target was a 99.99% pure Cu disk. An 8 cm in di...

In this work the study of the laser plasma generated from a Cu target by a XeCl excimer laser and the characteristics of the laser beam profile are described. The laser plasma is produced by focusing a low energy laser beam (70 mJ) onto the solid target by a 15 cm convergent lens. The laser spot was analyzed by scanning transversally the laser beam...

In this article we describe the design and the experimental results of a circuit able to compress a rectangular pulse causing its amplitude to increase. Utilizing a pulse forming line of 12 m long and a storage line of 6 m, both connected on a load resistor by means of fast transistor switch, a time compression factor of 2 was achieved. Charging th...

A novel type of current pulse compression circuit is realized utilizing transmission lines (TLs) and relatively fast switches. It yielded a time compression factor of?2 on a low load impedance. A 12?m, 50?? coaxial TL provided a current pulse of 3?A and 120?ns width. Adding a 6?m, 50?? storage line, able to store 50% of the initial pulse, and a f...

(1). To determine the biological effectiveness of two solar ultraviolet (UVB) spectra with different lower wavelength thresholds for oncogenic transformation and micronucleus induction in CGL1 cells; (2). to investigate whether the action spectra for short- and long-term effects are similar; and (3). to investigate possible links between transforma...

The new Synchrotron Radiation facility at Frascati exploits the intense photon emission from DAFNE, the 0,51 GeV storage ring circulating over 1 A of electrons. Among the three beamlines commissioned, the Synchrotron INfrared Beamline At Dafne (SINBAD) is fully operational by a brilliant SR beam spanning the entire IR. Recently, the soft X-ray beam...

In this work a new circuit to compress a pulse current utilizing transmission lines and transistor switches is proposed. It demonstrated a time compression factor of 2 on a low load impedance. A 12 m, 50Ω coaxial transmission line provided a current pulse of 3 A, 120 ns. A 6 m, 50Ω storage line connected to main line was able to store the 50% of th...

Published data on inactivation of V79 cells irradiated with monoenergetic proton and ion beams (He, C, O, Ne) have been analysed. Values for RBEa, RBE10% and the inactivation cross section s have been evaluated in the LET range between 5 and 400 keV.µm-1. RBE against LET curves and inactivation cross sections against LET and against Z*2/ß2 curves h...

To determine the effectiveness of two UV spectra with different UVB components for cell kill and micronucleus induction in irradiated human HeLaxskin fibroblast (CGL1) hybrid cells and their progeny. To determine the presence of reactive oxygen species (ROS) in the progeny of the irradiated cells at various post-irradiation times and their relation...