Traveling-Wave Thomson-Scattering for brilliant and efficient optical free-electron lasers

In Traveling-Wave Thomson-Scattering (TWTS) a high-power laser pulse is scattered off a relativistic electron pulse to produce radiation from EUV to Angstrom wavelength. TWTS employs a side-scattering geometry where laser and electron propagation direction enclose an angle to become independent of the Rayleigh length limit for the maximum interaction distance in standard head-on Thomson scattering geometries. For optimum spatial overlap in TWTS geometries the laser pulse features a pulse-front tilt. In this way, the electrons interact with all parts of the laser pulse and brilliances as well as photon scattering efficiencies are by orders of magnitude larger than in standard head-on geometries.
Interaction distances in TWTS are long enough for operation of a free-electron laser.
We show how TWTS experiments can be designed, present experimental parameters for TWTS FELs and discuss experimental challenges in their realization.