2 results
The SPARC/X SASE-FEL Projects
- D. ALESINI, S. BERTOLUCCI, M.E. BIAGINI, R. BONI, M. BOSCOLO, M. CASTELLANO, A. CLOZZA, G.. DI PIRRO, A. DRAGO, A. ESPOSITO, M. FERRARIO, V. FUSCO, A. GALLO, A. GHIGO, S. GUIDUCCI, M. INCURVATI, C. LIGI, F. MARCELLINI, M. MIGLIORATI, C. MILARDI, A. MOSTACCI, L. PALUMBO, L. PELLEGRINO, M. PREGER, P. RAIMONDI, R. RICCI, C. SANELLI, M. SERIO, F. SGAMMA, B. SPATARO, A. STECCHI, A. STELLA, F. TAZZIOLI, C. VACCAREZZA, M. VESCOVI, C. VICARIO, M. ZOBOV, F. ALESSANDRIA, A. BACCI, I. BOSCOLO, F. BROGGI, S. CIALDI, C. DE MARTINIS, D. GIOVE, C. MAROLI, V. PETRILLO, M. ROMÈ, L. SERAFINI, P. MUSUMECI, M. MATTIOLI, L. CATANI, E. CHIADRONI, S. TAZZARI, F. CIOCCI, G. DATTOLI, A. DORIA, F. FLORA, G.P. GALLERANO, L. GIANNESSI, E. GIOVENALE, G. MESSINA, L. MEZI, P.L. OTTAVIANI, L. PICARDI, M. QUATTROMINI, A. RENIERI, C. RONSIVALLE, A. CIANCHI, C. SCHAERF, J.B. ROSENZWEIG
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- Journal:
- Laser and Particle Beams / Volume 22 / Issue 3 / July 2004
- Published online by Cambridge University Press:
- 01 July 2004, pp. 341-350
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- Article
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SPARC and SPARX are two different initiatives toward an Italian Free Electron Laser (FEL) source operating in the Self Amplified Spontaneous Emission (SASE) mode, in which several national research institutions are involved. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting the SASE mechanism. An advanced Photo-Injector system, emittance compensating RF-gun plus a 150 MeV Linac, will inject a high quality e-beam into the undulator to generate high brilliance FEL radiation in the visible region at the fundamental wavelength, (∼500 nm). The production of flat top drive laser beams, high peak current bunches, and emittance compensation scheme will be investigated together with the generation of higher harmonic radiation in the VUV region. SPARX is the direct evolution of such a high gain SASE FEL toward the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. To get the required value for the bunch peak current, Ipeak ≈ 2.5 kA, the “hybrid” scheme, RF-compression stage plus magnetic chicane, is analyzed and compared with the more standard double stage of magnetic compression. The two options are reviewed considering the tolerance to the drive laser pulse phase jitter.
A simple hydro-elastic model of the dynamics of a vitreous membrane
- R. REPETTO, I. GHIGO, G. SEMINARA, C. CIURLO
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- Journal:
- Journal of Fluid Mechanics / Volume 503 / 25 March 2004
- Published online by Cambridge University Press:
- 01 March 2004, pp. 1-14
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We study the motion of a fluid within a rigid spherical container subject to small-amplitude periodic rotations. The sphere is divided into two equal portions by an impermeable stretched elastic membrane whose boundary is attached to the container wall. The model aims to represent in a simplified fashion the dynamics of a vitreous membrane subject to microsaccadic movements of the human eye, assuming the vitreous to be liquefied. The vitreous is modelled as a Newtonian, incompressible fluid in irrotational motion and the problem is linearized, taking advantage of the hypothesis of small-amplitude eye rotations. Results show that, due to the presence of the fluid, the natural frequencies of oscillation of the membrane decrease significantly with respect to the case of a free membrane. Moreover, oscillations of a stretched membrane are found to be resonantly excited by rotations of the sphere with frequencies which are typical of microsaccadic eye movements. This study suggests the possibility that oscillations of vitreous membranes may induce the development of large tensile stresses capable of producing a retinal detachment. Such a conclusion will have to be further substantiated by more refined analyses accounting for further effects, such as nonlinearity and the possible viscoelastic behaviour of the vitreous located on one or both sides of the membrane.