Wave optical description of the Traveling-Wave Thomson-Scattering optical undulator field and its application to the TWTS-FEL

We show that X-ray optical free electron lasers (OFELs) can be realized using Traveling Wave Thomson Scattering (TWTS) In TWTS pulse front tilted laser pulses are scattered off relativistic electron bunches in a side-scattering geometry. The pulse-front tilt guarantees overlap between laser and electrons over distances in the meter range while both are traveling in different directions. An interaction distance of 90 cm is obtained in a setup were 590 MeV electrons scatter off a petawatt class laser incident under an angle of 4.5 degrees. The amplification of the 1.5 angstrom radiation saturates at the end of the interaction. In order to account for spatial and temporal dispersion introduced with the pulse front tilt, we develop an exact three-dimensional analytical description of TWTS pulses that can be used in three-dimensional simulations of the radiation amplification process. The wave-optical formulation of the TWTS pulse includes dispersion to all orders and provides a general description of laser pulses diffracted at VLS gratings. (C) 2013 Elsevier B.V. All rights reserved