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Search Results: 1 - 10 of 219496 matches for " C. Spezzani "
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Experimental demonstration of frequency pulling in single-pass free-electron lasers
E. Allaria,C. Spezzani,G. De Ninno
Physics , 2011, DOI: 10.1364/OE.19.010619
Abstract: Frequency pulling is a well-known phenomenon in standard laser physics, leading to a shift of the laser frequency when the cavity and maximum gain frequencies are detuned. In this letter we present the first experimental demonstration of frequency pulling in single-pass free-electron lasers. Measurements are performed using the single-pass free-electron laser installed on the Elettra storage ring.
Angular Distribution of Nonlinear Harmonic Generation in Helical Undulators: a comparison between experiments and theory
E. Allaria,G. De Ninno,G. Geloni,C. Spezzani
Physics , 2011, DOI: 10.1016/j.nima.2011.06.034
Abstract: Using harmonic emission from circularly polarized undulator is a procedure that is normally employed on synchrotron beamlines in order to extend the covered spectral range. A similar capability is likewise beneficial for next generation free-electron lasers. In this paper, we perform a first quantitative experimental analysis of the angular distribution of free-electron laser harmonic emission from helical undulators. Experimental results are compared to those obtained by means of a theoretical model based on the paraxial solution of Maxwell's equations.
VUV and X-ray coherent light with tunable polarization from single-pass free-electron lasers
C. Spezzani,E. Allaria,B. Diviacco,E. Ferrari,G. Geloni,E. Karantzoulis,B. Mahieu,M. Vento,G. De Ninno
Physics , 2011, DOI: 10.1103/PhysRevLett.107.084801
Abstract: Tunable polarization over a wide spectral range is a required feature of light sources employed to investigate the properties of local symmetry in both condensed and low-density matter. Among new-generation sources, free-electron lasers possess a unique combination of very attractive features, as they allow to generate powerful and coherent ultra-short optical pulses in the VUV and X-ray spectral range. However, the question remains open about the possibility to freely vary the light polarization of a free-electron laser, when the latter is operated in the so-called nonlinear harmonic-generation regime. In such configuration, one collects the harmonics of the free-electron laser fundamental emission, gaining access to the shortest possible wavelengths the device can generate. In this letter we provide the first experimental characterization of the polarization of the harmonic light produced by a free-electron laser and we demonstrate a method to obtain tunable polarization in the VUV and X-ray spectral range. Experimental results are successfully compared to those obtained using a theoretical model based on the paraxial solution of Maxwell's equations. Our findings can be expected to have a deep impact on the design and realization of experiments requiring full control of light polarization to explore the symmetry properties of matter samples.
Fully-tunable femtosecond laser source in the ultraviolet spectral range
B. Mahieu,S. Coraggia,C. Callegari,M. Coreno,G. De Ninno,M. Devetta,F. Frassetto,D. Garzella,M. Negro,C. Spezzani,C. Vozzi,S. Stagira,L. Poletto
Physics , 2011,
Abstract: We demonstrate experimentally the full tunability of a coherent femtosecond source in the whole ultraviolet spectral region. The experiment relies on the technique of high-order harmonic generation driven by a near-infrared parametric laser source in krypton gas. By tuning the drive wavelength in the range between 1100 to 1900 nm, we generated intense harmonics from near to extreme ultraviolet. A number of photons per shot of the order of 10^7 has been measured for the first harmonic orders. Many novel scientific prospects are expected to benefit from the use of such a table-top tunable source.
X-ray method to study temperature-dependent stripe domains in MnAs/GaAs(001)
R. Magalhaes-Paniago,L. N. Coelho,B. R. A. Neves,H. Westfahl Jr.,F. Iikawa,L. Daweritz,C. Spezzani,M. Sacchi
Physics , 2004, DOI: 10.1063/1.1844599
Abstract: MnAs films grown on GaAs (001) exhibit a progressive transition between hexagonal (ferromagnetic) and orthorhombic (paramagnetic) phases at wide temperature range instead of abrupt transition during the first-order phase transition. The coexistence of two phases is favored by the anisotropic strain arising from the constraint on the MnAs films imposed by the substrate. This phase coexistence occurs in ordered arrangement alternating periodic terrace steps. We present here a method to study the surface morphology throughout this transition by means of specular and diffuse scattering of soft x-rays, tuning the photon energy at the Mn 2p resonance. The results show the long-range arrangement of the periodic stripe-like structure during the phase coexistence and its period remains constant, in agreement with previous results using other techniques.
CITIUS: an IR-XUV light source for fundamental and applied ultrafast science
C. Grazioli,C. Callegari,A. Ciavardini,M. Coreno,F. Frassetto,D. Gauthier,D. Golob,R. Ivanov,A. Kivim?ki,B. Mahieu,Bojan Bucar,M. Merhar,P. Miotti,L. Poletto,E. Polo,B. Ressel,C. Spezzani,G. De Ninno
Physics , 2013, DOI: 10.1063/1.4864298
Abstract: We present the main features of CITIUS, a new light source for ultrafast science, generating tunable, intense, femtosecond pulses in the spectral range from IR to XUV. The XUV pulses (about 10^5-10^8 photons/pulse in the range 14-80 eV) are produced by laser-induced high-order harmonic generation in gas. This radiation is monochromatized by a time-preserving monochromator, allowing also to work with high-resolution bandwidth selection. The tunable IR-UV pulses (10^{12}-10^{15} photons/pulse in the range 0.4-5.6 eV) are generated by an optical parametric amplifier, which is driven by a fraction of the same laser pulse that generates high order harmonics. The IR-UV and XUV pulses follow different optical paths and are eventually recombined on the sample for pump-probe experiments. The new light source will become the fulcrum of a new center located at the University of Nova Gorica, active in a wide range of scientific fields, including materials science, catalysis, biochemistry and magnetism. We also present the results of two pump-probe experiments: with the first one, we fully characterized the temporal duration of harmonic pulses in the time-preserving configuration; with the second one, we demonstrated the possibility of using CITIUS for studying of ultra-fast dynamics.
Magnetic reconfiguration of MnAs/GaAs(001) observed by Magnetic Force Microscopy and Resonant Soft X-ray Scattering
L. N. Coelho,R. Magalh?es-Paniago,B. R. A. Neves,F. C. Vicentin,H. Westfahl Jr.,R. M. Fernandes,F. Iikawa,L. D?weritz,C. Spezzani,M. Sacchi
Physics , 2006, DOI: 10.1063/1.2356794
Abstract: We investigated the thermal evolution of the magnetic properties of MnAs epitaxial films grown on GaAs(001) during the coexistence of hexagonal/orthorhombic phases using polarized resonant (magnetic) soft X-ray scattering and magnetic force microscopy. The results of the diffuse satellite X-ray peaks were compared to those obtained by magnetic force microscopy and suggest a reorientation of ferromagnetic terraces as temperature rises. By measuring hysteresis loops at these peaks we show that this reorientation is common to all ferromagnetic terraces. The reorientation is explained by a simple model based on the shape anisotropy energy. Demagnetizing factors were calculated for different configurations suggested by the magnetic images. We noted that the magnetic moments flip from an in-plane mono-domain orientation at lower temperatures to a three-domain out-of-plane configuration at higher temperatures. The transition was observed when the ferromagnetic stripe width L is equal to 2.9 times the film thickness d. This is in good agreement with the expected theoretical value of L = 2.6d.
X-ray holographic imaging of magnetic order in meander domain structures
Spezzani Carlo,Popescu Horia,Fortuna Franck,Delaunay Renaud
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134001001
Abstract: We performed x-ray holography experiments using synchrotron radiation. By analyzing the scattering of coherent circularly polarized x-rays tuned at the Co-2p resonance, we imaged perpendicular magnetic domains in a Co/Pd multilayer. We compare results obtained for continuous and laterally confined films.
Two-colour generation in a chirped seeded Free-Electron Laser
B. Mahieu,E. Allaria,D. Castronovo,M. B. Danailov,A. Demidovich,G. De Ninno,S. Di Mitri,W. M. Fawley,E. Ferrari,L. Fr?hlich,D. Gauthier,L. Giannessi,N. Mahne,G. Penco,L. Raimondi,S. Spampinati,C. Spezzani,C. Svetina,M . Trovò,M . Zangrando
Physics , 2013, DOI: 10.1364/OE.21.022728
Abstract: We present the experimental demonstration of a method for generating two spectrally and temporally separated pulses by an externally seeded, single-pass free-electron laser operating in the extreme-ultraviolet spectral range. Our results, collected on the FERMI@Elettra facility and confirmed by numerical simulations, demonstrate the possibility of controlling both the spectral and temporal features of the generated pulses. A free-electron laser operated in this mode becomes a suitable light source for jitter-free, two-colour pump-probe experiments.
ВПЛИВ Х М ЧНОГО СКЛАДУ НА ТИСК НАСИЧЕНО ПАРИ В МОТОРНИХ Б ОЛОГ ЧНИХ ПАЛИВАХ The influence of chemical composition on the saturated vapor pressure in biological motor fuels Влияние химического состава на давление насыщенного пара в моторных биологических топливах
?.В. Полунк?н,C.О. Зубенко,О.О. Гайдай,А.В. Струнгар
Proceedings of National Aviation University , 2010,
Abstract: Розглянуто вплив випаровуваност альтернативних палив на р шення проблеми холодного пуску двигуна за рахунок використання пропан-бутаново сум ш для п двищення тиску насичено пари. Volatility fuels fraction of the estimated parameters and letkosti. Volatility characterizes the ability to switch fuels in vaporous state. Selecting indicators to assess the volatility depends on the chemical composition of fuel. The main measure letkosti etanolnogo fuel is vapor pressure. The most simple and cost-effective to improve cold start is putting in fuel lehkoletyuchyh components: butane, izopentanu, gas and other petroleum. It was investigated the influence of DEE on alcohol-gasoline blend, the results show that DEE positive impact on increasing vapor pressure to the desired minimum for starting the engine. But because the ether to 19%, then at such high levels can actively formed peroxide compounds, which is undesirable. Very promising is the use of propane-butane gas mixture as lehkoletyuchoyi gaseous component. Butanizovani spirit-petrol mixture can be recommended for use as alternative fuel vehicles after further study of their stability and himmotolohichnyh characteristics. Автомобильные бензины и альтернативные биологические топлива на основе этанола преимущественно предназначены для применения в двигателях внутреннего сгорания. При использовании альтернативного биологического топлива, особенно этанольного, возникает проблема недостаточной испаряемости бензина при низкой температуре, в результате чего в холодное время года двигатель может не запуститься. Пусковые свойства бензина зависят от содержания в них летучих фракций или летучих соединений. Проблему холодного запуска предлагается решать за счет использования пропан-бутановой смеси для повышения давления насыщенного пара. Для перспективного применения газов пропан-бутановой смеси легколетучего газообразного компонента необходимы дальнейшие исследования стабилизации такой композиции.
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