Redshifting and harmonic radiation in the nonlinear laser-thomson scattering interaction

Thomson scattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also serves as a laboratory for strong field physics and nonlinear interactions. We present high resolution angle and energy resolved measurements on the laser-Thomson x-ray 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. As we increase the laser intensity, the electrons start to move in more complex trajectories resulting to emission of x-ray photons at higher harmonics which extends beyond 24 keV. Furthermore the overall radiation spectrum shows the broadening and redshift effect as predicted in the theory of intense laser-relativistic electron interaction in the classical picture. The amount of scattered photon also increases one order of magnitude to 106 photons per shot in the full opening emission angle.