• C. Vaccarezza, E. Chiadroni, M. Ferrario
  INFN/LNF, Frascati (Roma)
• G. Dattoli, L. Giannessi, M. Quattromini, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• M. Migliorati
  Rome University La Sapienza, Roma
• M. Venturini
  LBNL, Berkeley, California

The effects of microbunching instability for the SPARX accelerator have been analyzed by means of different numerical simulation codes and analytical approach. The laser heater counteracting action has been also addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.

• M. Ferrario, D. Alesini, F. A. Anelli, M. Bellaveglia, M. Boscolo, L. Cacciotti, M. Castellano, E. Chiadroni, L. Cultrera, G. Di Pirro, L. Ficcadenti, D. Filippetto, S. Fioravanti, A. Gallo, G. Gatti, A. Mostacci, E. Pace, R.S. Sorchetti, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• A. Bacci, V. Petrillo, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• A. Cianchi, B. Marchetti
  INFN-Roma II, Roma
• L. Giannessi, A. Petralia, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• O. Limaj
  University of Rome La Sapienza, Rome
• M. Moreno, M. Serluca
  INFN-Roma, Roma
• J.B. Rosenzweig
  UCLA, Los Angeles, California
• H. Tomizawa
  JASRI/SPring-8, Hyogo-ken
• C. Vicario
  PSI, Villigen

The primary goal of the SPARC project is the commissioning of the SASE FEL operating at 500 nm driven by a 150-200 MeV high brightness photoinjector. Additional experiments are foreseen also in the HHG Seeded configuration at 266, 160 and 114 nm. A second beam line hosting a THz source has been recently commissioned. The recent successful operation of the SPARC injector in the Velocity Bunching (VB) mode has opened new perspectives to conduct advanced beam dynamics experiments with ultra-short electron pulses able to extend the THz spectrum and to drive the FEL in the SASE Single Spike mode. Moreover a new technique called Laser Comb, able to generate a train of short pulses with high repetition rate, as the one required to drive coherent plasma wake field excitation, has been tested in the VB configuration. The energy/density modulation produced by an infrared laser pulse interacting with the electron beam near the cathode has been also investigated. In this paper we report the experimental results obtained so far and the comparison with simulations.