Does electron dynamics in Traveling-Wave Thomson-Scattering allow for an optical FEL?

In the Travelling-wave Thomson-scattering (TWTS) scheme ultrashort and narrow-band light pulses in the X-Ray region of the spectrum are created by scattering high intensity laser pulses from relativistic electron bunches. TWTS uses lasers with a pulse front tilt in a side-scattering geometry to scale the interaction length into the centimeter to meter range. This is crucial for allowing the scattered radiation to act back on the electrons which eventually can lead to coherent amplification of the radiation as in a free electron laser (FEL). We study the electron dynamics in the laser field including back reaction effects and discuss the applicability of TWTS as a SASE-FEL.