All-optical free-electron lasers with Traveling-Wave Thomson-Scattering

In Travelling-Wave Thomson Scattering (TWTS) the pulse front of a high-power, short-pulse laser is tilted and the dispersion of the pulse is controlled in such a way that electrons can interact over a long distance with a quasi-monochromatic electromagnetic wave. We present a complete three dimensional analytic time-dependent description of the TWTS field and use this description to derive an analytic FEL equation that shows that TWTS indeed provides for an all-optical FEL. We further derive conditions for optimum operation of the TWTS FEL, showing that EUV and XUV FEL sources are in reach using Petawatt lasers and conventional few-hundred MeV electron sources. Future laser-wakefield accelerators could potentially drive all-optical TWTS-FELs in the X-ray and beyond. TWTS itself is optimum to provide full flexibility in terms of the wavelength and bandwidth of the scattered radiation, allowing for application-optimized, highly-brilliant Thomson Scattering sources for a broad range of wavelengths from the EUV to the gamma ray spectral region.