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

The modeling of the microbunching instability has been carried out for the SPARX FEL accelerator, two configurations have been considered and compared: hybrid compression scheme (velocity bunching plus magnetic compressor) and purely magnetic. The effectiveness of a laser heather in reducing this instability drawbacks on the electron beam quality has also been exploited. Analytical predictions and start to end simulation results are reported in this paper.

• M. Ferrario, D. Alesini, M. Bellaveglia, M. Benfatto, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, A. Marcelli, A. Marinelli, C. Marrelli, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, R. Ricci, U. Rotundo, C. Sanelli, F. Sgamma, B. Spataro, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario
  INFN/LNF, Frascati (Roma)
• A. Bacci, I. Boscolo, F. Broggi, F. Castelli, S. Cialdi, C. De Martinis, D. Giove, C. Maroli, V. Petrillo, A.R. Rossi, L. Serafini
  Istituto Nazionale di Fisica Nucleare, Milano
• M. Bougeard, B. Carré, D. Garzella, M. Labat, G. Lambert, H. Merdji, P. Salières, O. Tchebakoff
  CEA, Gif-sur-Yvette
• L. Catani, A. Cianchi, B. Marchetti
  INFN-Roma II, Roma
• F. Ciocci, G. Dattoli, M. Del Franco, A. Dipace, A. Doria, G.P. Gallerano, L. Giannessi, E. Giovenale, G.L. Orlandi, S. Pagnutti, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I.P. Spassovsky, V. Surrenti
  ENEA C.R. Frascati, Frascati (Roma)
• M.-E. Couprie
  SOLEIL, Gif-sur-Yvette
• M. Mattioli, M. Serluca
  INFN-Roma, Roma
• M. Rezvani Jalal
  University of Tehran, Tehran
• J.B. Rosenzweig
  UCLA, Los Angeles, California

The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in SASE, Seeding and Single Spike configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous and stimulated radiation in the SPARC undulators. In this paper we report the experimental results obtained so far. The possible future energy upgrade of the SPARC facility to produce UV radiation and its possible applications will also be discussed.

Slides

• E. Hemsing, A. Marinelli, P. Musumeci, J.B. Rosenzweig, R. Tikhoplav
  UCLA, Los Angeles, California
• A. Gover
  University of Tel-Aviv, Faculty of Engineering, Tel-Aviv
• S. Reiche
  PSI, Villigen

The resonant harmonic interaction of an electron beam (e-beam) with an EM input field in a helical undulator is explored. The e-beam is coupled to the input radiation field at frequency harmonics through transverse gradients in the EM field, and helical micro-bunching of the e-beam is shown to occur naturally at the higher harmonics with the injection of a simple gaussian laser mode onto a cylindrically symmetric e-beam. This approach is under investigation as a method to generate a strongly pre-bunched e-beam seed for superradiant emission of light that carries orbital angular momentum in a downstream free-electron laser.