Giannessi, L.
(Luca Giannessi)

TUCOS04 Coherent Harmonic Generation using the ELETTRA Storage Ring Optical Klystron
Giovanni De Ninno, Miltcho B. Danailov, Bruno Diviacco, Mario Ferianis, Mauro Trovò (Elettra, Basovizza, Trieste), Luca Giannessi (ENEA C.R. Frascati, Frascati - Roma)

The standard process leading to CHG using single-pass devices or storage rings is based on the up-frequency conversion of a high-power laser focused into the first undulator of an optical klystron. The seeding signal, which is necessary to produce the modulation of the electron density and hence to induce the coherent emission, may be provided by an external laser or, in the case of storage-ring oscillators, by the FEL itself. The latter configuration has been recently implemented at ELETTRA allowing to generate the third harmonic of an intra-cavity signal at 660 nm. In the first part of this paper, we report about the set of measurements that have been performed, for different experimental set-ups, with the aim of characterizing the power as well as the spectral and temporal characteristics of the obtained radiation. As for seeding using an external laser, a detailed campaign of simulations, reported in the second part of the paper, shows that the ELETTRA optical klystron is also well suited for the investigation of this configuration. These results make the ELETTRA FEL an ideal test-facility in view of CHG experiments planned on dedicated next-generation devices.

MOPOS21 Seeding High Gain Harmonic Generation with Laser Harmonics Produced in Gases
Guillaume Lambert, Bertrand Carré, Yann Mairesse, Pascal Salières (CEA/Saclay, Gif-sur-Yvette), Marie-Emmanuelle Couprie, David Garzella (CEA/SPAM, Gif-sur-Yvette), Andrea Doria, Luca Giannessi (ENEA C.R. Frascati, Frascati - Roma), Toru Hara, Hideo Kitamura, Tsumoru Shintake (RIKEN Spring-8, Hyogo)

Free electron Lasers employing High Gain Harmonic generation (HGHG) schemes are very promising coherent ligth sources for the soft X-ray regime. They offer both transverse and longitudinal coherence, while Self Amplified Spontaneous Emission schemes have a longitudinal coherence limited. We propose here to seed HGHG with high harmonics produced by a Ti:Sa femtosecond laser focused on a gas jet, tuneable in the 100-10 nm spectral region. Specifities concerning the implementation of this particular laser source as a seed for HGHG are investigated. Semi analytical , numerical 1D and 3D calculations are given, for the cases of the SCSS, SPARC and ARC-EN-CIEL projects.

MOPOS26 Harmonic Generation and Linewidth Narrowing in Seeded FELs
Luca Giannessi (ENEA C.R. Frascati, Frascati - Roma)

The process of harmonic generation in a seeded single pass Free Electron Laser are studied in the time/frequency domain. The linewidth narrowing of the fundamental harmonic is correlated to the amplitude of the input seed. The spectral evolution of the harmonics is studied within a self consistent time dependent model.

MOPOS27 Status Report on SPARC Project
Alberto Renieri, Mariano Carpanese, Franco Ciocci, Giuseppe Dattoli, Antonio Di Pace, Andrea Doria, Francesco Flora, Gian Piero Gallerano, Luca Giannessi, Emilio Giovenale, Giovanni Messina, Luca Mezi, Pier Luigi Ottaviani, Simonetta Pagnutti, Giovanni Parisi, Luigi Picardi, Marcello Quattromini, Giuseppe Ronci, Concetta Ronsivalle, Elio Sabia, Mauro Sassi, Alberto Zucchini (ENEA C.R. Frascati, Frascati - Roma), Carlo Joseph Bocchetta, Miltcho B. Danailov, Gerardo D'Auria, Mario Ferianis (Elettra, Basovizza, Trieste), F. Alessandria, A. Bacci, Ilario Boscolo, F. Broggi, S. Cialdi, C. De Martinis, D. Giove, C. Maroli, V. Petrillo, M. Romè, Luca Serafini (INFN Milano, Milano), D. Levi, Mario Mattioli, G. Medici, Pietro Musumeci (INFN Roma, Roma), L. Catani, E. Chiadroni, Sergio Tazzari (INFN-Roma2, Roma), David Alesini, M. Bellaveglia, Sergio Bertolucci, M.E. Biagini, Caterina Biscari, R. Boni, Manuela Boscolo, Michele Castellano, A. Clozza, G. Di Pirro, A. Drago, A. Esposito, Massimo Ferrario, D. Filippetto, V. Fusco, A. Gallo, A. Ghigo, Susanna Guiducci, M. Incurvati, C. Ligi, F. Marcellini, Mauro Migliorati, C. Milardi, Luigi Palumbo, L. Pellegrino, Miro Preger, P. Raimondi, R. Ricci, C. Sanelli, Mario Serio, F. Sgamma, Bruno Spataro, A. Stecchi, A. Stella, Franco Tazzioli, Cristina Vaccarezza, Mario Vescovi, C. Vicario, M. Zobov (INFN/LNF, Frascati (Roma)), A. Cianchi, A. D'Angelo, R. Di Salvo, A. Fantini, D. Moricciani, Carlo Schaerf (Rome University Tor Vergata, Roma), D. H. Dowell, Paul J Emma, C. Limborg-Deprey, D. T. Palmer (SLAC, Menlo Park, California), James B Rosenzweig, Gil Travish (UCLA, Los Angeles, California), Sven Reiche (UCLA/DPA, Los Angeles - California)

We review the status of FEL source activity of the on going SPARC FEL experiment, developed within the framework of a collaboration among ENEA, CNR, INFN, INFM, Sincrotrone Trieste and University of Rome Tor Vergata. The project is aimed at realising a SASE FEL source, operating in the visible (around 500 nm), with an extended range of tunability down to the VUV (100nm) by the use of the mechanism of non-linear harmonic generation. The development of the relevant activities foresees the realisation of an advanced 150 MeV photo-injector source, aimed at producing a high brightness electron beams, needed to drive a SASE-FEL experiment and a 12 m long undulator. We present the status of the design and construction of the injector, of the undulator and of the e-beam transport line. In particular we discuss the choice of the project parameters, their optimisation and the sensitivity of the SPARC performance to any parameter variation. We will show, using start to-end simulations, what is the impact of the e-beam and of the undulator parameters on the characteristics of the output laser field and in particular on the amount of the non linearly generated power at higher harmonics.

THPOS09 Electron-Beam Stabilization for the European Storage-Ring Free-Electron Laser at Elettra
Mauro Trovò, Daniele Bulfone, Miltcho B. Danailov, Giovanni De Ninno, Bruno Diviacco, Vincenzo Forchi`, Marco Lonza (Elettra, Basovizza, Trieste), Luca Giannessi (ENEA C.R. Frascati, Frascati - Roma)

The temporal structure of the storage-ring free-electron laser at Elettra shows high sensitivity to electron-beam instabilities. In fact, even small beam orbit oscillations (of the order of few microns) may perturb the FEL dynamics and periodically switch off the laser. In order to improve the FEL operation and performance, a longitudinal multi-bunch feedback and a local orbit feedback have been activated. This paper reports on the beneficial effect of these feedback systems. Plans for a future "slow" longitudinal feedback are also briefly described.

TUPOS11 The SPARX Project : R&D Activity towards X-rays FEL Sources
David Alesini, M. Bellaveglia, Sergio Bertolucci, M.E. Biagini, R. Boni, Manuela Boscolo, Michele Castellano, A. Clozza, G. Di Pirro, A. Drago, A. Esposito, Massimo Ferrario, D. Filippetto, V. Fusco, A. Gallo, A. Ghigo, Susanna Guiducci, M. Incurvati, C. Ligi, F. Marcellini, Mauro Migliorati, Andrea Mostacci, Luigi Palumbo, L. Pellegrino, Miro Preger, P. Raimondi, R. Ricci, C. Sanelli, Mario Serio, F. Sgamma, Bruno Spataro, A. Stecchi, A. Stella, Franco Tazzioli, Cristina Vaccarezza, Mario Vescovi, C. Vicario (INFN/LNF, Frascati (Roma)), Franco Ciocci, Giuseppe Dattoli, Antonio Di Pace, Andrea Doria, Francesco Flora, Gian Piero Gallerano, Luca Giannessi, Emilio Giovenale, Giovanni Messina, Luca Mezi, Pier Luigi Ottaviani, Simonetta Pagnutti, Giovanni Parisi, Luigi Picardi, Marcello Quattromini, Alberto Renieri, Concetta Ronsivalle, A. Torre, Alberto Zucchini (ENEA C.R. Frascati, Frascati - Roma), F. Alessandria, A. Bacci, Ilario Boscolo, F. Broggi, S. Cialdi, C. De Martinis, D. Giove, C. Maroli, M. Mauri, V. Petrillo, M. Romè, Luca Serafini (INFN Milano, Milano), Mario Mattioli, Pietro Musumeci (INFN Roma, Roma), L. Catani, E. Chiadroni, A. Cianchi, Carlo Schaerf (INFN-Roma2, Roma), S. De Silvestri, M. Nisoli, S. Stagira (Politecnico di Milano, Milano), Paul J Emma (SLAC, Menlo Park, California), James B Rosenzweig (UCLA, Los Angeles, California), Sven Reiche (UCLA/DPA, Los Angeles - California)

SPARX is an evolutionary project proposed by a collaboration among ENEA-INFN-CNR-Università di Roma Tor Vergata aiming at the construction of a FEL-SASE X-ray source in the Tor Vergata Campus. The first phase of the SPARX project, funded by Government Agencies, will be focused on the R&D activity on critical components and techniques for future X-ray facilities. The R&D plans for the FEL source will be developped along two lines: (a) use of the SPARC high brightness photo-injector to develop experimental test on RF compression techniques and other beam physics issues, like emittance degradation in magnetic compressors due to CSR; (b) development of new undulator design concepts and up-grading of the FEL SPARC source to enhance the non linear harmonic generation mechanism, design and test of e-beam conditioning, prebunching and seeding. A parallel program will be aimed at the development of high repetition rate S-band gun, high Quantum Efficiency cathodes, high gradient X-band RF accelerating structures and harmonic generation in gas. In a second phase we plan to explore production of X-rays in a SASE-FEL with harmonic generation, upgrading existing facilities.

TUPOS12 Spectral Analysys of Charge Emission Spatial Inhomogeneities and Emittance Dilution in RF Guns
Marcello Quattromini, Luca Giannessi, Concetta Ronsivalle (ENEA C.R. Frascati, Frascati - Roma)

The effects of fluctuations in cathode's quantum efficiency and other sources of dishomogeneities in the performances of a typical RF photoinjector have been investigated with TREDI numerical simulations. The RF gun layout includes a focusing solenoid in a configuration aimed at minimizing the emittance growth due to space charge effects.