Cultrera, L.
Gatti, G.
Tazzioli, F.
Perrone, A.
Miglietta, P.
Ristoscu, C.
Orlanducci, S.
Fiori, A.
Advanced high brightness radio frequency (RF) gun injectors require photocathodes with a fast response, high quantum efficiency (QE) and good surface uniformity. Metal films deposited by various techniques on the gun back wall could satisfy these requirements. A new deposition technique has been recently proposed, i.e. pulsed laser ablation. Several Mg samples have been deposited by this technique: the emission performance and morphological changes induced on the cathode surface during laser activation are compared and discussed. (C) 2007 Elsevier B.V. All rights reserved.
Maisonnier, D.
Amelotti, F.
Chiasera, A.
Gaggini, P.
Damiani, C.
Degli Esposti, L.
Gatti, G.
Castillo, E.
Caravati, D.
Farfalletti-Casali, F.
Gritzmann, P.
Ruiz, E.
The remote replacement of blanket segments inside the vacuum vessel of a fusion reactor is probably the most complex task from the maintenance standpoint. Its success will rely on the definition of appropriate handling concepts and equipment, but also on a ldquomaintenance friendlyrdquo reactor layout and blanket design. The key difficulty is the lack of rigidity of the segments which results in considerable deformations since they cannot be gripped above their centre of gravity. These deformations may be up to five times greater than the assembly clearance and one order of magnitude larger than the required positioning accuracy. Experimental activities have been undertaken to select appropriate handling devices and procedures, to assess the design of the components handled, and to review specific technical issues such as kinematics and dynamics performance, trajectory planning and control and sensors requirement for the handling devices. Work was performed in the Robertino facility where two handling concepts have been tested at a 1/3 scale
Roth, S.
Crepaldi, A.
Puppin, M.
Gatti, G.
Bugini, D.
Grimaldi, I
Barrilot, T. R.
Arrell, C. A.
Frassetto, F.
Poletto, L.
Chergui, M.
Marini, A.
Grioni, M.
With its tunable band-gap and its unique optical and electronic properties black phosphorus (BP) opens exciting opportunities for optoelectronic nanotechnology. The band-gap extends from the visible to the mid-infrared spectral range, as a function of sample thickness and external parameters such as electric field and pressure. This, combined with the saturable absorption and in-plane anisotropic optical properties, makes BP a versatile platform for realizing polarization-sensitive photodetectors and absorbers. Although its near-equilibrium properties have been intensively studied, the development of efficient ultrafast optical devices requires detailed knowledge of the temporal dynamics of the photoexcited hot-carriers. Here we address the electronic response of BP to an ultrafast laser excitation, by means of time-and angle-resolved photoelectron spectroscopy. Following the optical excitation, we directly observe a shift of the valence band (VB) position, indicative of band-gap renormalization (BGR). Our data also show that the hole population in the VB relaxes with a characteristic time tau(VB) =3D 10.2 +/- 1.0 ps, while the lifetime of the electrons accumulated at the minimum of the conduction band is tau(CB) =3D 1.9 +/- 0.2 ps. The experimental results are well reproduced by ab initio calculations of the out-of-equilibrium electronic properties. Our study sets the reference for the ultrafast carrier dynamics in BP and demonstrates the material's ultrafast BGR, which is promising for optoelectronic switches.
Bacci, A.
Broggi, F.
DeMartinis, C.
Giove, D.
Maroli, C.
Petrillo, V.
Rossi, A. R.
Serafini, L.
Tomassini, P.
Cultrera, L.
Di Pirro, G.
Ferrario, M.
Filippetto, D.
Gatti, G.
Pace, E.
Vaccarezza, C.
Vicario, C.
Bosi, F.
Giulietti, D.
Gizzi, L. A.
Oliva, P.
The PLasma Acceleration and MONochromatic X-ray generation (PLASMONX) project foresees the installation at LNF of a 0.3 PW (6 J, 20 fs pulse) Ti:Sa laser system, named Frascati Laser for Acceleration and Multidisciplinary Experiments (FLAME), to operate in close connection with the existent SPARC electron photo-injector, allowing for advanced laser/e-beam interaction experiments. Among the foreseen scientific activities, a Thomson scattering experiment between the SPARC electron bunch and the high power laser will be performed. At the present time the linac has been tested and the electron beam characterized up to the maximum operating energy (150 MeV). The beam lines transporting the beam to the interaction chamber with the laser have been designed. The electron final focusing system, featuring a quadrupole triplet and large radius solenoid magnet (ensuring an e-beam waist of 5-10 mu m) as well as the whole interaction chamber layout has been defined. The optical transfer line issues: transport up to the interaction; tight focusing; diagnostics and fine positioning; have been solved within the final design. The construction of the building hosting the laser has been completed: delivering and installation of the laser, as much of the beam lines elements will take place in the next months. (C) 2009 Elsevier B.V. All rights reserved.
We propose a decoherence protected protocol for sending single photon quantum states through depolarizing channels. This protocol is implemented via an approximate quantum adder engineered through spontaneous parametric down converters, and shows higher success probability than distilled quantum teleportation protocols for distances below a threshold depending on the properties of the channel.
Labate, L.
Anelli, F.
Bacci, A.
Batani, D.
Bellaveglia, M.
Benedetti, C.
Benocci, R.
Cacciotti, L.
Cecchetti, C. A.
Ciricosta, O.
Clozza, A.
Cultrera, L.
Di Pirro, G.
Drenska, N.
Faccini, R.
Ferrario, M.
Filippetto, D.
Gallo, S.
Fioravanti, S.
Gamucci, A.
Gatti, G.
Ghigo, A.
Giulietti, A.
Giulietti, D.
Koester, P.
Levato, T.
Lollo, V.
Pace, E.
Pathak, N.
Rossi, A.
Serafini, L.
Turchetti, G.
Vaccarezza, C.
Valente, P.
Vicario, C.
Gizzi, L. A.
A 250-TW laser system (FLAME - Frascati laser for acceleration and multidisciplinary experiments) is now in its commissioning phase in a new laboratory at LNF-INFN in the framework of the PLASMONX (Plasma acceleration and monochromatic X-ray generation) project. The laser will deliver25fs duration pulses with an energy up to 6J, at a 10Hz repetition rate. An ad hoc target area has also been designed and is currently being set up, allowing the first test experiments of electron laser wakefield acceleration to be carried out over the next few months in a safe, radiation-protected environment. An overview of the main features of the laser system and target area is given, along with a survey of the design and set-up of the self-injection test experiment, which is expected to reach the production of sub-GeV electron bunches.
Cianchi, A.
Anania, M. P.
Bellaveglia, M.
Bisesto, F.
Castellano, M.
Chiadroni, E.
Di Giovenale, D.
Di Pirro, G.
Ferrario, M.
Gatti, G.
Mostacci, A.
Pompili, R.
Shpakov, V.
Stella, A.
Villa, F.
Advanced diagnostic tools for high brightness electron beams are mandatory for the proper optimization of plasma-based accelerators. The accurate measurement of beam parameters at the exit of the plasma channel plays a crucial role in the fine tuning of the plasma accelerator. Electron beam diagnostics will be reviewed with emphasis on emittance measurement, which is particularly complex due to large energy spread and strong focusing of the emerging beams.
Sutter, D.
Fatuzzo, C. G.
Moser, S.
Kim, M.
Fittipaldi, R.
Vecchione, A.
Granata, V.
Sassa, Y.
Cossalter, F.
Gatti, G.
Grioni, M.
Ronnow, H. M.
Plumb, N. C.
Matt, C. E.
Shi, M.
Hoesch, M.
Kim, T. K.
Chang, T. -R.
Jeng, H. -T.
Jozwiak, C.
Bostwick, A.
Rotenberg, E.
Georges, A.
Neupert, T.
Chang, J.
A paradigmatic case of multi-band Mott physics including spin-orbit and Hund's coupling is realized in Ca2RuO4. Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic structure. Here we provide-using angle-resolved photoemission electron spectroscopy-the band structure of the paramagnetic insulating phase of Ca2RuO4 and show how it features several distinct energy scales. Comparison to a simple analysis of atomic multiplets provides a quantitative estimate of the Hund's coupling J =3D 0.4 eV. Furthermore, the experimental spectra are in good agreement with electronic structure calculations performed with Dynamical Mean-Field Theory. The crystal field stabilization of the d(xy) orbital due to c-axis contraction is shown to be essential to explain the insulating phase. These results underscore the importance of multi-band physics, Coulomb interaction and Hund's coupling that together generate the Mott insulating state of Ca2RuO4.
Petrarca, M.
Musumeci, P.
Mattioli, M. C.
Vicario, C.
Gatti, G.
Ghigo, A.
Cialdi, S.
Boscolo, I.
In the SPARC photoinjector, the amplified Ti:Sa laser system is conceived to produce an UV flat top pulse profile required to reduce the beam emittance by minimizing the non-linear space charge effects in the photoelectrons pulse. Beam dynamic simulations indicate that the optimal pulse distribution must be flat top in space and time with 10 ps FWHM duration, I ps of rise and fall time and a limited ripple on the plateau. In a previous work(1) it was demonstrated the possibility to use a programmable dispersive acousto-optics (AO) filter to achieve pulse profile close to the optimal one. In this paper we report the characterization of the effects of harmonies conversion on the pulse temporal profile. A technique to overcome the harmonics conversion distortions on the laser pulses at the fundamental wavelength in order to obtain the target pulse profile is explained too. Measurements and simulations in the temporal and spectral domain at the fundamental laser wavelength and at the second and third harmonics are presented in order to validate our work. It is also described a time diagnostic device for the UV pulses.
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