Tunable X-rays generation in a free-electron laser by intracavity Compton backscattering

A nearly monochromatic X-ray beam of 7 to 12 keV has been produced by intracavity Compton backscattering in the CLIO infrared free-electron laser. The X-rays were extracted by a Berillyum made cavity mirror. The spectrum has been measured by scanning the X-ray line across the K edge of a thin metal foil. This shows that the FEL intracavity scheme for the Compton backscattering is very efficient since the intracavity FEL power is much higher than any other tunable laser can produce, and can lead to the generation of usable picosecond X-ray beams.