• S. Di Mitri, E. Allaria, R. Appio, L. Badano, D. Castronovo, M. Cornacchia, P. Craievich, S. Ferry, L. Froehlich, S.V. Milton, G. Penco, C. Scafuri, C. Spezzani, M. Trovò, M. Veronese
  ELETTRA, Basovizza
• R. Bartolini
  Diamond, Oxfordshire
• G. De Ninno, S. Spampinati
  University of Nova Gorica, Nova Gorica
• P. Evtushenko
  JLAB, Newport News, Virginia
• W.M. Fawley
  LBNL, Berkeley, California
• L. Giannessi
  ENEA C.R. Frascati, Frascati (Roma)
• A.A. Lutman
  DEEI, Trieste
• M. Sjöström
  MAX-lab, Lund

Some experiences have recently been collected from the FERMI@elettra Free Electron Laser first bunch compressor area. This includes a magnetic compressor, diagnostics for the characterization of the longitudinal and transverse phase space and suitable optics for matching to the downstream part of the linac. We report on the beam dynamics investigations in comparison with the modeling as well as the high level software control that has allowed this experience.

• S. Di Mitri, S. Ferry
  ELETTRA, Basovizza

Horizontal scraping, geometric and energy collimation of the Fermi@elettra electron beam has been investigated analytically and with the elegant particle tracking code. Beam scraping in the first magnetic bunch length compressor has been characterized in terms of reduction of the transverse emittance and variation of the energy chirp induced by the succeeding linac longitudinal wake field. The locations of the geometric and energy collimators have been identified in the machine lattice. A novel definition of collimation efficiency is proposed that allowed us to identify a configuration of the collimation system that is a compromise between the collimation performance, optics design and available space.

• M. Veronese, R. Appio, T. Borden, G. Ciani, P. Craievich, R. De Monte, S. Di Mitri, M. Ferianis, G. Gaio, S. Grulja, G. Scalamera, M. Tudor
  ELETTRA, Basovizza

Both absolute and relative bunch length measurement are key information for FERMI@Elettra commissioning and operation. In this paper we present the relative Bunch Length Monitor (BLM) system that has been designed and implemented at Sincrotrone Trieste. The first BLM station has been installed downstream the first bunch magnetic compressor (BC1) of FERMI@Elettra. In this paper we report about the first operation of the BLM system; it is based on the power measurement of the coherent radiations. To allow for efficient performances in the extended range of the foreseen bunch lengths for FERMI@Elettra, the system has adopted a pyro detector for coherent edge radiation from the last dipole. Also, the coherent diffraction radiation generated in a ceramic gap located downstream of BC1 is detected by a set of mm-wave diodes. The design of the system, along with its layout, is presented as well as the first measurement results obtained from the FERMI@Elettra compressed bunches.

• S. Di Mitri, M. Cornacchia
  ELETTRA, Basovizza

The optics design of the first bunch compressor area in the FERMI@elettra linac is presented. Several constraints on the Twiss parameters are set by the preservation of beam quality in the first magnetic compressor, the optimization of diagnostics performance, the collimation process and the beam matching to the downstream lattice. A compact multi-purpose arrangement of magnetic and diagnostic elements is presented that, in principle, satisfies several different needs over a total length of 14m.

• S. Di Mitri, M. Cornacchia, P. Craievich, G. Penco
  ELETTRA, Basovizza
• S. Spampinati
  University of Nova Gorica, Nova Gorica
• M. Venturini, A. Zholents
  LBNL, Berkeley, California

Two machine configurations of the electron beam dynamics in the FERMI@elettra linac have been investigated, namely the one-stage and the two-stage electron bunch compression. One of the merits of the one-stage compression is that of minimizing the impact of the microbunching instability on the slice energy spread and peak current fluctuations at the end of the linac. Special attention is given to the manipulation of the longitudinal phase space, which is strongly influenced by the linac structural wake fields. The electron bunch with a ramping peak current is used in order to obtain, at the end of the linac, an electron bunch characterized by a flat peak current profile and a flat energy distribution. Effects of various jitters on electron bunch energy, arrival time and peak current are compared and relevant tolerances are obtained.

• S. Di Mitri, M. Cornacchia
  ELETTRA, Basovizza
• W.A. Barletta
  LBNL, Berkeley, California

Simulations of the microbunching instability through the FERMI@elettra lattice have been carried out with elegant particle tracking code. This paper focuses on the emittance growth induced by the microbunching instability in the high energy transfer line that guides the electron beam from the linac to the undulator chain. The perturbation to the transverse emittance induced by coherent synchrotron radiation and longitudinal space charge as function of the R56 transport matrix element in the transfer line have been investigated separately and in the presence of their mutual interaction. Simulation results show that the betatron phase mismatch may have a detrimental impact on the final beam emittance.