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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 209Bi were prepared. The disks were irradiated in a high-flux reactor to transmute the 209Bi into 210Po. After the irradiation, the 210Po activity was measured for all four disks. While two of the disks were stored at room temperature, the other two disks were stored in a sealed container submerged in liquid helium (T = 4.2 K) for approximately 200 days. After the storage time the 210Po-activity measurements were repeated and the 210Po half-life was calculated for each sample. No difference between the half-lives for the four samples could be detected within the uncertainties of the measurements. In other words, the results of this study show no evidence for an increase of activity for α emitters embedded in a metallic matrix at very low temperature.

Due to the diffusion of severe pathogens, everyday life is exposed to the risks of contracting severe diseases. For this reason, efficient antimicrobial surfaces are of paramount importance. In this work we present the first evidences of a new technique to obtain an antibacterial ultra high molecular weight polyethylene based on a non- stoichiometric, visible light responsive, titanium oxide coating. The coating was obtained through a process in which titanium ions, resulting from laser ablation of a corresponding target, were accelerated and implanted on the samples. The samples were tested against a Staphylo- coccus aureus strain, in order to assay their antimicrobial efficacy. Results show that this treatment strongly dis- courages bacterial colonization of the treated surfaces.

The production of proton beams by ns low intensity pulsed excimer laser ablation of solid hydrogenated targets is investigated. The targets used were solid disks produced by compression of TiH2 and CaH2 powder. The ion emission was analyzed by the time-of-flight (TOF) technique using a Faraday Cup as ion collector. We performed preliminary studies on the produced plasma in free expansion mode and under an accelerating voltage up to 15 kV, for different laser fluence values. The TOF spectra deconvolution through Maxwell-Boltzmann shifted function permitted us to evaluate the plasma temperature, particle density, ion charge state distributions, proton and ion energy and their relative yield. Using these special targets, we were able to obtain protons, titanium and calcium ion beams with a kinetic energy of some tens of keV.

Ion production

Emittance study of an accelerated ion beam provided by laser ablation

We report characteristics of ion emission from Cu, Sn, Cu/Sn4, Cu/Be2, Ag/Cu7.5 and Ag/Cu28 plasmas generated by a KrF laser which was operated at a wavelength of 248 nm and delivered energy up to 50 mJ. The time-of-flight characteristics of ion beams were determined by using a Faraday cup. The employment of an expansion chamber, a new part of the experimental apparatus, allows to accelerate the created ion beam by HV potential up to 40 kV and to investigate the evolution of ToF signals at a distance. The analysis of ion characteristics is the main scope of our contribution. An influence of the dopant admixture, laser pulse energy and accelerating potential on the characteristics of the ion emission is demonstrated.

Laser ion sources offer the possibility to get ion beam utilizable to improve particle accelerators. Today many laboratories, as well as the LEAS, are employed to develop accelerators of the dimensions very contained to be installed in little laboratories and hospitals. Pulsed lasers at intensities of the order of 108 W/cm2 and of ns pulse duration interacting with solid matter in vacuum, plasma of high temperature and density is produced. The charge state distribution of the plasma generates high electric fields which accelerate ions along the normal to the target surface. The energy of emitted ions has a Maxwell Boltzmann distribution which depends on the ion charge state. To increase the ion energy, a post-acceleration system can be employed by means of high voltage power supplies of about 100 kV. The post acceleration system results a good method to obtain high ion currents by a not expensive system and the final ion beams find interesting applications in the field of the ion implantations, adrotherapy, scientific applications and industrial use. In this work we compare the electromagnetic and geometric properties, like the emittanza, of the beams delivered by a Cu and Y target. The characterization of the plasma was performed by a Faraday cup for the electromagnetic characteristics, whereas a pepper pot system for the geometrical ones. At 60 kV accelerating voltage and 5.5 mA output current the normalized beam emittance resulted of 0.22 π mm mrad for the Cu target, while under the same accelerating voltage but with 7.4 mA output current a lower normalized beam emittance value was reached for the Y target. It resulted of 0.14 π mm mrad. The brightness of the beams was of 114 and 378 mA( mm mrad)-2 for the Cu and Y target, respectively. When Ag targets were utilised, we implanted an AISI 420 stainless steel by a dose of 10x1015 inos/cm2. Besides, the laser ion sources have got very good properties to feed large machines.

In questo lavoro si presentano i risultati ottenuti impiantando ioni di Cu e Ag su polietilene Ultra High Molecular Weight Polyethylene. L'impiantazione è stata eseguita utilizzando la tecnica LIS (Laser Ion Source), con laser ad eccimeri KrF e utilizzando una doppia accelerazione ottendo 60 kV di accelerazione. La fluenza laser è stata di 2.2 J/cm2 corrispondente ad un flusso ionico di 1012 ions/cm2 . Test di antibattericità sono stati condotti utilizzando il ceppo Staphylococcus aureus. Esami preliminari dimostrano una diminuzione della proliferazione di batteri sui campioni trattati.

I fasci di ioni di alcune centinaia di kV di energia e di buona qualità geometrica sono oggi utilizzati in diversi settori applicativi per la modifica di materiali da drogaggio. Per generare sorgenti di ioni, un metodo moderno ed alternativo che viene presentato in questo lavoro è la tecnica dell'ablazione laser. L'acceleratore realizzato è un dispositivo compatto in grado di ottenere fasci ionici da laser plasma con energie sino a 160 keV per stato di carica. È stata condotta una caratterizzazione del fascio (energia, stato di carica, divergenza, emittanza, corrente) supportata dall'uso di un software di simulazione, Comsol Multiphysics.

Studies on Vibrio bacteria sampled from a coastal cave having an high radon content are presented. Most of the strains exhibited a low rate of survival after the UV exposure. All strains after UV and visible irradiation showed an high capability of photoreactivation. This capability was unexpected. We hypothesize that the photoreactivation might have been evolved to repair DNA lesions induced also by different radiations and that the luminescent bacteria might use their own light emission to carry out the photoreactivation. We assessed that the photoreactivation increased for some strains of about 42000 times.

Bio-luminescent bacteria exposed to radiation of UHTM frequencies is not known and they offer new prospective to study modern biological sensors and DNA. We performed experiments undergoing an electric field of 53 and 140 V/m. Bioluminescence decreased of 77% and 68% undergone lower and higher electric field, respectively. We estimated a corresponding enhancement of the bioluminescent activity of bacteria growing at RF environment of 23 and 85 times undergone lower and higher electric field. This behavior of intense activity of bacteria on RF exposure can be ascribed to the anti-mutagenic effect of the RF.

Bacteria undergoing environmental effects is extremely interesting for structural, mechanistic, and evolutionary implications. Luminescent bacteria that have evolved in a specific ambient have developed particular responses and their behavior can give us new suggestions on the task and production of luciferina proteins. To analyze the UV interaction under controlled laboratory conditions, we used photoluminescent bacterial strains belonging to a new species evolutionarily close to Vibrio harveyi sampled from a coastal cave with a high radon content that generates ionizing radiation. The survival of the bacterial strains was analyzed, in the light and in the dark, following a variety of genotoxic treatments including UV radiation exposure. The strains were irradiated by a germicide lamp. The results demonstrated that most of the strains exhibited a low rate of survival after the UV exposure. After irradiation by visible light following the UV exposure, all strains showed a high capability of photoreactivation when grown. This capability was quite unexpected because these bacteria were sampled from a dark ambient without UV radiation. This leads us to hypothesize that the photoreactivation in these bacteria might have been evolved to repair DNA lesions also induced by different radiation sources other than UV (e.g., x-ray) and that the luminescent bacteria might use their own light emission to carry out the photoreactivation. The high capability of photoreactivation of these bacteria was also justified by the results of deconvolution. The deconvolution was applied to the emission spectra and it was able to show evidence of different light peaks. The presence of the visible peak could control the photolysis enzyme.

In this work, we report on the characterization of pulsed soft X-rays emitted from laser-produced plasma by different targets. The measurements were performed in a vacuum stainless-steel chamber at 10-7 mbar .The plasma was generated by a pulsed KrF excimer laser of 248 nm laser wavelength, operating at single shot and having a pulses of 23 ns FWHM. The beam was focused on pure Si, Cu and Ta targets. The laser energies were 40, 80 and 120 mJ, concentrated onto a spot of about 0.01 cm2, with a resulting irradiance of 1.7, 3.5 and 5.2x108 Wcm-2. The utilized detector was a very sensitive Faraday cup which opportunely biased was able to record time resolved signals of X-rays and to estimate their energy. The found X-rays energy values were compared to the ion temperature of the target plasma fitting the time resolved ion current signals by the shifted Maxwell-Boltzmann velocity distribution.

We developed an ion accelerator with a double accelerating gap system supplied by two power generators of different polarity.-The ions were generated by laser ion source technique. The laser plasma induced by an excimer KrF laser, freely expanded before the action of accelerating fields. After the first gap action, the ions were again accelerated by a second gap. The total acceleration can imprint a maximum ion energy up to 160 keV per charge state. We analyzed the extracted charge from a Cu target as a function of the accelerating voltage at laser energy of 9, 11 and 17 mJ deposited on a spot of 0.005 cm2. The peak of current density was 3.9, 5.3 mA for the lower and medium laser energy at 60 kV. At the highest laser energy, the maximum output current was 11.7 mA with an accelerating voltage of 50 kV. The maximum ion dose was estimated to be of 1012 ions/cm2. Under the condition of 60 kV accelerating voltage and 5.3 mA output current the normalized emittance of the beam measured by pepper pot method was 0.22 π mm mrad.

In this work two different techniques to modify the polymeric surfaces are compared; Laser irradiation and ion implantation were performed on Ultra High Molecular Weight Polyethylene (UHMWPE) samples. The irradiation treatment was performed by using two different laser sources operating in the UV and IR range, applying many laser shots in air atmosphere on the polymer surface. Ion implantation was performed using a new LIS (Laser Ion Source) accelerator with an accelerating voltage of 40 kV. Contact angle, roughness and Fourier Transform Infra Red (FT-IR) measurements were performed on the samples before and after the two treatments in order to obtain information on the UHMWPE modification.