High order Harmonics
HHG (high order harmonics generation) process
When an intense femtosecond driving laser (visible to IR) pulse intercepts a gas-jet or a gas cell filled with Ar, Ne, Kr,… electrons can be extracted from the atoms through tunnel ionization, gain energy in the laser electric field, and recombine with the parent atoms by emitting harmonics of the driving laser, XUV light or X-rays.
Details on the HHG process can be found in literature, see for example T. Popmintchev, M.-C. Chen, P. Arpin, M. M. Murnane and H. C. Kapteyn, Nat. Photonics 4 (2010) 822.
Based on this, a system to generate and monochromatize XUV pulses was built.
Depending on the choice of the gas acting as non linear medium, it is possible to generate XUV pulses in the (20-80 eV) spectral region with a fluence of 10^6 photons/pulse.
Description of the beam-line can be found here.