Petawatt Class Lasers for Realizing Optical Free-Electron Lasers with Traveling-Wave Thomson-Scattering

Traveling-Wave Thomson-Scattering (TWTS) is a scheme for the realization of optical free-electron lasers (OFELs) from the interaction of ultra-short, high-power laser pulses with relativistic electrons.
The laser pulse thereby provides the undulator field which typically needs to include a few 100 to several 1000 undulator periods for OFEL operation.
Such long optical undulators are realized in TWTS by the combination of a side-scattering geometry where electron and laser pulse propagation directions enclose the interaction angle $\phi$ and a laser pulse-front tilt $\alpha_\A{tilt} = \phi/2$ of half the interaction angle.
This combination of side-scattering and pulse-front tilt ensures continuous overlap of electrons and laser pulse during the passage of the electrons through the laser pulse.
Interaction durations between laser pulse, electrons, and their emitted radiation can be long enough to initiate microbunching of the electron pulse and subsequent coherent amplification of radiation provided electron and laser pulse are of sufficient quality.
Requirements on electron and laser pulse quality can be met for VUV TWTS OFELs with existing technology already today and higher power laser pulses enable TWTS OFELs at shorter wavelength, e.\,g.\ EUV TWTS OFELs.