• 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.

• W.M. Fawley, J.-L. Vay
  LBNL, Berkeley, California

Numerical electromagnetic simulation of some systems containing charged particles with highly relativistic directed motion can by sped up by orders of magnitude by choice of the proper Lorentz-boosted frame*. A particularly good application for boosted frame calculation is short wavelength FEL simulation. In the optimal boost frame (i.e., the ponderomotive rest frame), the red-shifted FEL radiation and blue-shifted undulator field have identical wavelengths and the number of required time-steps for fully electromagnetic simulation (relative to the laboratory frame) decreases by a factor of gamma squared. We have adapted the WARP code** to apply this method to several FEL problems including coherent spontaneous emission from prebunched e-beams, strong exponential gain in a single pass amplifier configuration, and FEL emission from e^- beams in undulators with multiple harmonic components. We discuss our results and compare with those obtained using the "standard" FEL simulation approach which applies the eikonal and wiggler-period-averaging approximations.

* J.-L. Vay, Phys. Rev. Lett. 98, 130405 (2007).
** D.P. Grote, A. Friedman, J.-L. Vay, and I. Haber, AIP Conf. Proc. 749, 55 (2005).

• W.M. Fawley
  LBNL, Berkeley, California
• K.-J. Kim, R.R. Lindberg, Yu. Shvyd'ko
  ANL, Argonne

The oscillator package within the GINGER FEL simulation code has now been extended to include angle-dependent reflectivity properties of Bragg crystals. Previously, the package was modified to include frequency-dependent reflectivity in order to model x-ray FEL oscillators[*] from start up from shot noise to saturation. We will present a summary of the algorithms used for modeling the crystal reflectivity and radiation propagation outside the undulator, discussing various numerical issues relevant to the domain of high Fresnel number and efficient Hankel transforms. We give some sample XFEL-O simulation results obtained with the angle-dependent reflectivity model, with particular attention directed to the longitudinal and transverse coherence of the radiation output.

[*] R.R. Lindberg et al., submitted to PRST-AB, 2010.