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Gatti, G.

Paper Title Page
MOOAAB02 Experimental Results with the SPARC Emittance-meter 80
 
  • M. Ferrario, D. Alesini, M. Bellaveglia, S. Bertolucci, R. Boni, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, M. Incurvati, C. Ligi, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario
    INFN/LNF, Frascati (Roma)
  • A. Bacci, S. Cialdi, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • L. Catani, E. Chiadroni, A. Cianchi
    INFN-Roma II, Roma
  • A. M. Cook, M. P. Dunning, P. Frigola, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • L. Giannessi, M. Quattromini, C. Ronsivalle
    ENEA C. R. Frascati, Frascati (Roma)
  • P. Musumeci, M. Petrarca
    INFN-Roma, Roma
  
  The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive a SASE-FEL in the visible light. As a first stage of the commissioning a complete characterization of the photoinjector has been done with a detailed study of the emittance compensation process downstream the gun-solenoid system. For this purpose a novel beam diagnostic device, called emittance meter, has been developed and used at SPARC. This device has allowed to measure the evolution of beam sizes, energy spread and rms transverse emittances at different location along the beamline, in the region where space-charge effects dominate the electron dynamics and the emittance compensation process takes place. In this paper we report our commissioning experience and the results obtained. In particular a comparison between the performances of a Gaussian laser pulse versus a Flat Top laser pulse will be discussed. We report also the first experimental observation of the double emittance minima effect on which is based the optimised matching with the SPARC linac.  
slides icon Slides  
TUPMN034 Comparison Between SPARC E-Meter Measurements and Simulations 986
 
  • C. Ronsivalle, L. Giannessi, M. Quattromini
    ENEA C. R. Frascati, Frascati (Roma)
  • A. Bacci, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • M. Boscolo, E. Chiadroni, M. Ferrario, D. Filippetto, V. Fusco, G. Gatti, M. Migliorati, A. Mostacci, C. Vaccarezza, C. Vicario
    INFN/LNF, Frascati (Roma)
  • A. Cianchi
    INFN-Roma II, Roma
  • M. Petrarca
    Universita di Roma I La Sapienza, Roma
  
  For the SPARC photoinjector commissioning the emittance compensation process has been studied experimentally under different beam conditions (variation of charge, spot size, beam shape…) by a novel device called "emittance-meter", consisting in a movable emittance measurement system based on the 1D pepper pot method scanning a region 1.2 m long downstream the RF-gun. The results of a detailed comparison between the measurements and beam dynamics simulations performed by the different codes(PARMELA, HOMDYN, TREDI) employed for SPARC design are presented and discussed here.  
TUPMN036 Laser and RF Synchronization Measurements at SPARC 992
 
  • A. Gallo, M. Bellaveglia, G. Gatti, C. Vicario
    INFN/LNF, Frascati (Roma)
  
  Funding: Work supported by the EU Commission in the sixth framework programme, contract no. 011935 - EUROFEL.

The SPARC project consists in a 150 MeV B-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been recently completed. During year 2006 a first experimental phase aimed at characterizing the beam emittance in the first 2m drift downstream the RF gun has been carried out. The low level RF control electronics to monitor and synchronize the RF phase in the gun and the laser shot on the photocathode has been commissioned and extensively tested during the emittance measurement campaign. The laser synchronization has been monitored by measuring the phase of the free oscillation of an RF cavity impulsively excited by the signal of a fast photodiode illuminated by the laser shot. Phase stability measurements are reported, both with and without feedback correction of the slow drifts. A fast intra-pulse phase feedback system to reduce the phase noise produced by the RF power station has been also positively tested.

 
TUPMN037 Power Tests of a PLD Film Mg Photo-cathode in a RF Gun 995
 
  • G. Gatti, L. Cultrera, F. Tazzioli
    INFN/LNF, Frascati (Roma)
  • J. Moody, P. Musumeci
    UCLA, Los Angeles, California
  • A. Perrone
    INFN-Lecce, Lecce
  
  Metallic film photo-cathodes are rugged, have a fast response and good emission uniformity. Mg has also a relevant Quantum Efficiency in the near UV. A cathode suitable for a 1.5 cells S-band RF gun has been produced by depositing an Mg film on Cu by Pulsed Laser Deposition technique. After different optimizations, stable good results have been reached in the low field measurement scenario. A sample was deposited on a gun flange and tested in the 1.6 cell injector at UCLA Pegasus facility to prove cathode resistence in a high field environment. The results are described.  
TUPMN038 Coherent Cherenkov Radiation as a Temporal Diagnostic for Microbunched Beams 998
 
  • G. Gatti
    INFN/LNF, Frascati (Roma)
  • A. M. Cook, J. B. Rosenzweig, R. Tikhoplav
    UCLA, Los Angeles, California
  
  Cherenkov radiation of a relativistic e-beam traversing a thin section of aerogel is analized, putting the stress on the coherent contribution due to the intra-beam, transverse and longitudinal structure. The use of this tool as a temporal diagnostic for micro-bunched beams makes possible to improve the amount of collected power at the microbunching frequency several orders of magnitude more respect to the uncoherent Cherenkov contribution. The non-idealities of a real beam are taken in account, and some techniques aimed on enhancing the coherent part of radiation are proposed and analized analitically and through simulation codes.  
TUPMN040 Drive Laser System for SPARC Photoinjector 1004
 
  • C. Vicario, M. Bellaveglia, D. Filippetto, A. Gallo, G. Gatti, A. Ghigo
    INFN/LNF, Frascati (Roma)
  • S. Cialdi
    INFN-Milano, Milano
  • P. Musumeci, M. Petrarca
    INFN-Roma, Roma
  
  In this paper we report the progress of the SPARC photoinjector laser system. In the high brightness photoinjector the quality of the electron beam is directly related to the photocathode drive laser. In fact the 3D distribution of the electron beam is determined by the incoming laser pulse. The SPARC laser is a 10 Hz frequency-tripled TW-class Ti:Sa commercial system. To achieve the required flat top temporal shape we perform a manipulation of the laser spectrum in the fundamental wavelength and in the third harmonic. The optical transfer-line has been implemented to limit the pointing instabilities and to preserve to the cathode the temporal and spatial features of the laser pulse. We present the recorded performances in terms of time pulse shape and rf-to-laser synchronization.  
TUPMS037 Simulation of an Iris-guided Inverse Free-electron Laser Micro-bunching Experiment 1266
 
  • J. T. Frederico, S. Reiche, R. Tikhoplav
    UCLA, Los Angeles, California
  • G. Gatti
    INFN/LNF, Frascati (Roma)
  
  The Free-Electron Laser code Genesis 1.3 has been modified to include waveguides within the undulator, reducing the diffraction effects for long wavelength FELs. Several types of waveguides are considered, which are rectangular and circular waveguides as well as iris-loaded open waveguides. Studies are presented here on the enhancement of FEL and IFEL with these wave-guiding structures in comparison to free-space propagation of the radiation wave.  
THPMS026 The UCLA Helical Permanent-Magnet Inverse Free Electron Laser 3055
 
  • R. Tikhoplav, J. T. Frederico, G. Reed, J. B. Rosenzweig, S. Tochitsky, G. Travish
    UCLA, Los Angeles, California
  • G. Gatti
    INFN/LNF, Frascati (Roma)
  
  The Inverse Free Electron Laser (IFEL) is capable, in principle, of reaching accelerating gradients of up to 1 GV/m making it a prospective accelerator scheme for linear colliders. The Neptune IFEL at UCLA utilizes a 15 MeV Photoinjector-generated electron beam of 0.5 nC and a CO2 laser with peak energy of up to 100 J, and will be able to accelerate electrons to 100 MeV over an 80 cm long, novel helical permanent-magnet undulator. Past IFELs have been limited in their average accelerating gradient due to the Gouy phase shift caused by tight focusing of the drive laser. Here, laser guiding is implemented via an innovative Open Iris-Loaded Waveguide Structure scheme which ensures that the laser mode size and wave front are conserved through the undulator. The results of the first phase of the experiment are discussed in this paper, including the design and construction of a short micro-bunching undulator, testing of the OILS waveguide, as well as the results of corresponding simulations.  
TUPMN039 Status of the SPARC-X Project 1001
 
  • C. Vaccarezza, D. Alesini, M. Bellaveglia, S. Bertolucci, R. Boni, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, C. Ligi, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, M. A. Preger, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stella, F. Tazzioli, M. Vescovi, C. Vicario
    INFN/LNF, Frascati (Roma)
  • F. Alessandria, A. Bacci, R. Bonifacio, I. Boscolo, F. Broggi, F. Castelli, S. Cialdi, C. De Martinis, A. F. Flacco, D. Giove, C. Maroli, V. Petrillo, A. R. Rossi, L. Serafini
    INFN-Milano, Milano
  • M. Bougeard, P. Breger, B. Carre, D. Garzella, M. Labat, G. Lambert, H. Merdji, P. Monchicourt, P. Salieres, O. Tcherbakoff
    CEA, Gif-sur-Yvette
  • L. Catani, E. Chiadroni, A. Cianchi, E. Gabrielli, C. Schaerf
    INFN-Roma II, Roma
  • F. Ciocci, G. Dattoli, A. Dipace, A. Doria, F. Flora, G. P. Gallerano, L. Giannessi, E. Giovenale, G. Messina, P. L. Ottaviani, S. Pagnutti, G. Parisi, L. Picardi, M. Quattromini, A. Renieri, G. Ronci, C. Ronsivalle, M. Rosetti, E. Sabia, M. Sassi, A. Torre, A. Zucchini
    ENEA C. R. Frascati, Frascati (Roma)
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • P. Emma
    SLAC, Menlo Park, California
  • M. Mattioli, D. Pelliccia
    Universita di Roma I La Sapienza, Roma
  • P. Musumeci, M. Petrarca
    INFN-Roma, Roma
  • C. Pellegrini, S. Reiche, J. B. Rosenzweig
    UCLA, Los Angeles, California
  • A. Perrone
    INFN-Lecce, Lecce
  
  SPARC-X is a two branch project consisting in the SPARC test facility dedicated to the development and test of critical subsystems such as high brightness photoinjector and a modular expandable undulator for SASE-FEL experiments at 500 nm with seeding, and the SPARX facility aiming at generation of high brightness coherent radiation in the 3-13 nm range, based on the achieved expertise. The projects are supported by MIUR (Research Department of Italian Government) and Regione Lazio. SPARC has completed the commissioning phase of the photoinjector in November 2006. The achieved experimental results are here summarized together with the status of the second phase commissioning plans. The SPARX project is based on the generation of ultrahigh peak brightness electron beams at the energy of 1 and 2 GeV generating radiation in the 3-13 nm range. The construction is at the moment planned in two steps starting with a 1 GeV Linac. The project layout including both RF-compression and magnetic chicane techniques has been studied and compared, together with the feasibility of a mixed s-band and x-band linac option.  
THPMS021 Optimum Electron Bunch Creation in a Photoinjector Using Space Charge Expansion 3044
 
  • J. B. Rosenzweig, A. M. Cook, M. P. Dunning, R. J. England, P. Musumeci
    UCLA, Los Angeles, California
  • M. Bellaveglia, M. Boscolo, G. Di Pirro, M. Ferrario, D. Filippetto, G. Gatti, L. Palumbo, C. Vicario
    INFN/LNF, Frascati (Roma)
  • L. Catani, A. Cianchi
    INFN-Roma II, Roma
  • S. M. Jones
    Jet Propulsion Laboratory, Pasadena, California
  
  Recent studies have shown that by illuminating a photocathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped electron bunch can be dynamically formed. Linear space-charge fields then exist in all dimensions inside of the bunch, which minimizes emittance growth. Here we study this process, and its marriage to the standard emittance compensation scenario that is implemented in most modern photoinjectors. We show that the two processes are compatible, with simulations indicating that a very high brightness beam can be obtained. An initial time-resolved experiment has been performed at the SPARC injector in Frascati, involving Cerenkov radiation produced at an aerogel. We discuss the results of this preliminary experiment, as well as plans for future experiments to resolve the ellipsoidal bunch shape at low energy. Future measurements at high energy based on fs resolution RF sweepers are also discussed.