Author: Yang, X.
Paper Title Page
Ultrashort Pulse Generation and Superradiance in FELs  
  • X. Yang
    BNL, Upton, Long Island, New York, USA
  • L. Giannessi
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  The generation of a single X-ray isolated spike of radiation with peak power at multi-GW level and femtosecond temporal duration represents an almost unique opportunity in time resolved diffraction imaging of isolated molecules or non-periodic structures, for the possibility of acquiring single shot images before the Coulomb explosion of the sample takes place. Such a condition is met by an FEL operating in superradiant regime when the pulse has a self-similar shape deriving from the combined dynamics of saturation and slippage of the radiation over fresh electrons. We show that the peak of the pulse moves at superluminal speed similarly to the case of pulses propagation in anomalous dispersive active media and it is followed by a long pedestal resulting from the complex dynamics occurring in the tail after saturation. We analyze the dynamical conditions leading to the formation of the main pulse and the following tail and we study the correlation of the tail structure with the longitudinal phase space of the e-beam, providing recipes to partially suppress it.  
slides icon Slides TUP1WA02 [5.300 MB]  
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