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•The article analyses the behaviour of a linear Rogowski coil applied to a flat transmission line for to study of electromagnetic stresses in biological samples.•To develop the ...theory, I use the Laplace Transform. The device will be useful when the 5G communication mode generates new electromagnetic radiation.
New developments on Rogowski coil are presented due to the evolution of temporal shortening of the current pulses. Recently, to study biophysical stresses by electromagnetic pulses flat transmission lines are used. As a result, linear Rogowski coils for electrical current diagnostics have also been developed and applied. An electrostatic shield with a slim slit is used to protect the Rogowski coil. The presence of the slit is necessary to lead the input current around the coil. The response of the Rogowski coil on high frequency signals is influenced, not only by all inductances, the capacitance, the number of turns of the coil, the load resistance, but also by the small size of the slim slit operated on the metal shield. The new theory is able to justify the response of the device due to sub-ns pulses, ~100ps, on slit width. By the theory, the attenuation factor is dependent on the slit size. This behaviour was experimentally verified obtaining a value ranging from 15.6A/V to 24.7A/V. The longest measurable pulse was approximately 250ns. The device is very interesting owing to the radiation of the 5G communication mode.
In this paper, we report a study on proton beams produced via laser interaction from hydrogenated solid targets useful for the development of new sources devoted to medical applications, such as ...hadron therapy and isotope production. The hydrogenation of the targets was made before the laser-matter interaction. In this study, we used as solid targets, pure samples of Ti, Ta and Al which in a first phase were treated by laser cleaning (via KrF excimer laser at the irradiance I = 3×107 W/cm2) and then they were exposed to laser irradiation (1500 pulses, I = 3×107 W/cm2}) under a constant flow of H2 (HiQ Hydrogen 6.0, highly pure). After that, the targets were maintained under H2 flow for 5 minutes, in order to promote a further hydrogen adsorption. We report laser ablation measurements performed at fluences of 1.3, 2.5 and 5.0 J/cm2. The results on hydrogenated targets showed an increase of proton yield of 25% (Ti), 64% (Al) and 550% (Ta), with respect to the corresponding untreated ones.
The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength,λ=248nm; photon energy,EPh=5eV) is reported. The ND ...layers were deposited by means of a pulsed spray technique. Specifically, the active layer of each PC consisted of untreated (as-received) and hydrogenated ND particles, 250 nm in size, sprayed on ap-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at10−6mbarand compared to a Cu-based one, used as reference. All the photocathodes were irradiated at normal incidence. The quantum efficiency (QE) of the photocathodes was assessed. QE values of the ND-based photocathodes were higher than that of the reference one. In particular, the hydrogenated ND-based PC exhibited the highest QE due to the negative electron affinity that results from the surface terminated by hydrogen. Additionally, the photocathode surface/local temperature and the multiphoton process contribution to the electron emission were studied.
In this work we report a study on the influence of innovative pulsed stresses utilizing an UV laser and a homemade generator of magnetic field on radish seeds (Raphanus sativus L.) growth. We ...analysed the seed germination and seedling growth. The UV pulsed laser was an excimer KrF operating at 248 nm, 23 ns of pulse duration, with a laser fluence of about 40 mJ/cm2. The generator of pulsed magnetic field was realized by the electric discharge on a coil of a high voltage capacitor of 150 μF, 60 kV . The magnetic field pulse waveform exhibited damped oscillations at 215 kHz with a maximum intensity of 400 mT . Groups of uniform radish seeds were exposed to laser pulses at five different doses: 30000 shots (KrF/1), 80000 shots (KrF/2), 145000 shots (KrF/3), 225000 shots (KrF/4) and 275000 shots (KrF/5). Other groups were exposed to magnetic field at eight different doses: 3600 shots (MF/1), 7200 shots (MF/2), 10800 shots (MF/3), 14400 shots (MF/4), 18000 shots (MF/5), 21600 shots (MF/6), 32400 kshots (MF/7) and 36000 shots (MF/8). Simultaneously, untreated seeds were used as control. All treatments were performed at room temperature. Both untreated and treated seeds were transferred in Petri dishes and followed for their germination and seedling growth up to 96 h. The results showed that the stress induced by UV laser photons brought a significant stimulation on root growth which may contribute to improve the performance and the productivity of the plants. On the contrary, all physical stresses induced by magnetic fields did not have effect on seed germination, as well as on cell elongation growth and on hypocotyls in comparison to control seeds.
In this work, the geometric and electromagnetic characteristics of electron beams generated by three photocathodes (PCs), two based on nanodiamond (ND) layers and one based on Cu (generally used as ...reference) were investigated. Specifically, the active layers of the ND-based PCs consisted of untreated and hydrogenated (H-ND) nanoparticles (250 nm in size) deposited by pulsed spray technique on p-doped silicon substrates as uniform coating. Photoemission measurements carried out by a KrF nanosecond excimer laser (λ = 248 nm) in a vacuum chamber at 10−6 mbar and the emittance evaluation, performed by the pepper pot method, are reported and discussed. For the last, radio-chromic films (HD-810 Gafchromic) were used as sensible screen for electrons. The study of the emittance was performed by varying the laser spot onto the PC surface and the accelerating voltage (5, 10 and 15 kV) . From emittance values, the normalized brightness was also estimated for all the cathodes. The obtained results showed quantum efficiency values of the ND-based photocathodes higher than that of the reference Cu one, but, at the same time, higher emittances and therefore worse performancers as the result of the enlarged beam divergence. Despite this, H-ND resulted to be the best PC between those investigated for the highest normalized beam brightness, thanks to its high electron current and low normalized emittance.
We reports a study on pure and Ni-doped TiO2 thin films produced via laser ablation technique. The novelty of the work consists that both synthesis and doping were carried out in a single process, ...using a modified laser ion source to simultaneously make pulsed laser deposition (PLD) and low-energy ion implantation (by post-acceleration method). In particular, two titania films were synthesized via PLD starting from a rutile target. One of the two films was doped with Ni ions, accelerated with a voltage of 20 kV. The total implanted dose, evaluated by a Faraday cup, resulted to be 1×1014 ions/cm2. The crystalline phase of the obtained TiO2 films was analysed by Raman spectroscopy. A higher photocatalytic activity, measured under UV irradiation using methylene blue, was estimated for the Ni-doped titania film with respect the pure one.
In this work, zebrafish (Danio rerio) embryos were subjected to different physical stresses, consisting of a static and two low frequency magnetic fields, and two radio frequencies. Specifically, ...embryos were exposed to static (Bo, 0 Hz), very low frequency (VLF, 0.2 Hz), low frequency (LF, 270 kHz), very high frequency (VHF, 100 MHz) and ultra-high frequency (UHF, 900 MHz) magnetic field irradiations for up to 5 days. The field intensities were 40 mT, 40 mT, 470 μT, 240 nT and 240 nT, respectively. Untreated embryos were used as control (n = 10 for each condition).
Proton extraction from transition metals using PLATONE Velardi, L.; Delle Side, D.; Kràsa, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2014, Letnik:
735
Journal Article
Recenzirano
In this work we present a study on proton beams extraction from a plasma generated by pulsed laser ablation of titanium and tantalum disks. The device used was the PLATONE laser ion source operating ...at the LEAS Laboratory in Lecce, Italy. It is based on a KrF laser operating at low irradiance (109-1010 W/cm2) and ns pulse duration. The proton and ions emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector and an electrostatic barrier to identify the particles. Studies on the produced protons and ions at different laser irradiance values were performed. The extracted beams showed high proton flux up to 1010 protons/cm2.
► Titanium Hydride powder represents a widely available and cheap material. ► It is easy to obtain solid disks by compression of this powder. ► UV laser ablation of these disks represents a valid ...source of low energy protons.
In this work we present the preliminary investigations about the production of proton beams by pulsed laser ablation of solid disks produced by compressed Titanium Hydride (TiH) powder. The laser we used was an excimer KrF, operating at low intensity and ns pulse duration. The ion emission was analyzed by the time-of-flight technique using a Faraday cup as ion collector. We performed initial studies on the produced plasma for different laser fluence values. In free expansion mode we obtained protons and titanium ions having kinetic energy of some hundred of eV; by applying a post-accelerating voltage we analyzed the beams up to 15keV.
Experimental results are obtained concerning the target polarization, which aptly characterizes the laser ablation. The charge separation in the laser-produced plasma, structure of the ion front, and ...the current of fast electrons expanding into the vacuum chamber ahead of ions are of crucial importance for the interpretation of multi-peak structure of target currents appearing much later than the laser pulse. Of particular interest is the correlation between the partial maxima in the time-resolved target current and the square root of mass number of ionized species. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer krypton fluoride laser.
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