Picosecond Narrow Bandwidth X-ray Pulses from a Laser-Thomson-Backscattering Source

Intense, ultimately coherent, ultrashort hard X-ray pulses can serve as a novel tool for structural analysis of complex systems with unprecedented temporal and spatial resolution. With the simultaneous availability of a high power short-pulse laser system it provides unique opportunities for a number of subsequent research steps at the forefront of relativistic light-matter interactions. At HZDR we demonstrated the generation of such a light source (PHOENIX) by colliding picosecond electron bunches from the ELBE linear accelerator with counter-propagating femtosecond laser pulses from the 150 TW Draco Ti:Sapphire laser system. The generated narrowband X-rays are highly collimated and can be reliable adjusted from 5.5 to 23.5 keV by tuning the electron energy (24 MeV to 30 MeV) and the laser intensity. Ensuring the spatiotemporal overlap and suppressing the bremsstrahlung background we have achieved a signal-to-noise ratio greater than 300:1. Together with the use of an X-ray camera (resolution of 250 eV(FWHM)) to record the spectrum, we were able to resolve the angular-energy correlation and to study the influence of the beam emittance on the observed bandwidth.