Self-consistently modeling Traveling-Wave Thomson-Scattering Optical Free-Electron Lasers

Traveling-Wave Thomson-Scattering (TWTS) provides optical undulators with hundreds to thousands of undulator periods from high-power, pulse-front tilted lasers pulses. These allow to realize optical free-electron lasers (OFELs) with state-of-the-art technology in electron accelerators and laser systems.
TWTS employs a side-scattering geometry where laser and electron propagation direction of motion enclose the interaction angle. Tilting the laser pulse front with respect to the wave front by half the interaction angle ensures continuous overlap over the whole laser pulse width while the electrons cross the laser beam path.
Scaling laws and analytical models allow identifying experimentally promising FEL regimes for feasible setup geometries. However, selfconsistently
including all non-ideal effects in a 3D FEL simulations is desirable for predicting TWTS-OFEL designs with quantitive performance and tolerance characteristics suitable for engineering an optimal proof-of-principle experiment. In this talk we outline the challenges that existing FEL codes cannot cope with the non-collinear geometry of TWTS-OFELs, show how we solve these using the particle-in-cell code PIConGPU as 3D-FEL code and present first results.