• V. Petrillo
  Universita' degli Studi di Milano, Milano
• A. Bacci, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• M. Boscolo, M. Ferrario, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• G. Dattoli, L. Giannessi, M. Labat, P.L. Ottaviani, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• S. Pagnutti
  ENEA-Bologna, Bologna
• L. Palumbo
  Rome University La Sapienza, Roma
• M. Serluca
  INFN-Roma, Roma

We describe a possible experiment aimed at generating sub-picosecond high brightness electron bunches with the SPARC photoinjector, which produce optical single spike radiation pulses in the regime of self-amplified spontaneous emission. The main purpose of the experiment is the production of short electron bunches as long as few SASE cooperation lengths by means of the Velocity Bunching technique. The measure of the properties of the electron beam, the determination of shape and spectrum of the radiation pulse and the validation of the single spike scaling laws will be analysed in order to foresee future operations at shorter wavelength with SPARX. We present in this paper start-to-end simulations of the beam production and FEL performance, statistical analysis and behaviour on the harmonics. The experience gained from this experiment will help in the configuration of the VUV and X-ray FEL SPARX to obtain FEL pulses below 10 fs.

• D. Filippetto, D. Alesini, M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, L. Cultrera, G. Di Pirro, M. Ferrario, L. Ficcadenti, V. Fusco, A. Gallo, G. Gatti, C. Marrelli, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, B. Spataro, C. Vaccarezza, C. Vicario
  INFN/LNF, Frascati (Roma)
• A. Bacci, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• A. Cianchi
  Università di Roma II Tor Vergata, Roma
• L. Giannessi, M. Labat, M. Quattromini, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• B. Marchetti
  INFN-Roma II, Roma
• J.B. Rosenzweig
  UCLA, Los Angeles, California
• M. Serluca
  INFN-Roma, Roma

The optimization of the beam brightness is one of the main objectives of the research and development efforts in rf-photoinjectors devoted to short wavelength FELs. The velocity bunching experiment at SPARC has recently demonstrated the possibility of increasing the beam current via RF compression at low energies, while compensating the self-fields induced emittance degradation by means of continuous magnetic focusing. The result is an increase of the beam brightness by about one order of magnitude. Stable compression ratio up to a factor 12 has been observed. Characterization of longitudinal phase spaces an measure of projected and slice emittances, as a function of the injection phase in the first accelerating structure and for different solenoids field values are presented. Comparisons with simulations are also reported.

Slides

• M. Labat, F. Ciocci, G. Dattoli, M. Del Franco, A. Doria, G.P. Gallerano, L. Giannessi, E. Giovenale, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I.P. Spassovsky, V. Surrenti
  ENEA C.R. Frascati, Frascati (Roma)
• D. Alesini, M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, M. Ferrario, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Mostacci, E. Pace, L. Palumbo, B. Spataro, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• F. Briquez, M.-E. Couprie
  SOLEIL, Gif-sur-Yvette
• B. Carré, D. Garzella
  CEA, Gif-sur-Yvette
• A. Cianchi, B. Marchetti
  INFN-Roma II, Roma
• G. Marcus, J.B. Rosenzweig
  UCLA, Los Angeles, California
• M. Mattioli, M. Serluca
  INFN-Roma, Roma

The SPARC FEL can be operated in both SASE and seeded modes. A major part of the second stage of the commissioning, currently in progress, is dedicated to the characterization of the SASE radiation. Simultaneously, we are finalizing the experimental setup for seeding. We present an in-situ characterization of the two input seeds that are foreseen: both are obtained via harmonic generation, the first one in crystal (400 and 266 nm) and the second in rare gas (Argon). We also describe the specific diagnostics implemented for the electron-seed overlap in the undulator, together with the diagnostics for radiation analysis (2D spectrometer and FROG). The seeding will enable the operation of the SPARC FEL in original cascaded configurations.