Correlation of electron and laser beam parameters to the spectral shape and bandwidth of laser-Thomson backscattering x-ray beams

Development of advanced x-ray sources based on laser-Thomson scattering mechanism is becoming important pushed by a strong demand for ultrashort hard x-ray pulses, which can serve as a novel tool for structural analysis of complex systems with unprecendented temporal and spatial resolution. The spectral shape and bandwidth of this x-ray beam is the result from the interplay between interacting electron and laser beam parameters. We present high resolution angle and energy resolved measurements on the x-ray photon distribution generated by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating laser pulses from the 150 TW DRACO Ti:Sapphire laser system. The measured data and an ab-initio comparison with the 3D radiation code CLARA enable us to reveal parameter influences and correlation of both interacting beams. We conclude that in the low laser intensity interaction regime the electron angular distribution and the laser bandwidth, as in the case of ultrashort laser pulses, give a strong influence to the x-ray spectral shape and bandwidth. We also show the x-ray spectral broadening as the laser intensity increases indicating nonlinear interaction on the scattering process. Controlling these parameters is necessary for designing future Thomson x-ray sources with a specific bandwidth suited to an application.