Compact X-ray free-electron laser based on an optical undulator

The interaction between a very high-brightness electron beam and a relativistically intense optical laser pulse produces X-rays via coherent Thomson back scattering with FEL collective amplification. The phenomenon is, however, very selective, so that the characteristics of both electron and laser beam must satisfy tight requirements in terms of beam current, emittance, energy spread and laser amplitude stability within the pulse. The three-dimensional equations governing the radiation phenomena have been studied in both linear and non-linear regime and solved numerically for the particularly interesting values of wavelengths of 1 Å, 1 and 12 nm. The performance of the collective Thomson source has been compared with that of an equivalent static undulator. A set of scaling laws ruling the phenomenon is also presented.