Optical Afterburner for a SASE FEL

The radiation produced by a Self-Amplified Spontaneous Emission Free Electron Laser (SASE FEL) leaves a specific energy pattern over the length of the radiating electrons. This pattern, the SASE Fingerprint, leads to a spikey energy structure modulation on the order of the coherence length on the electron bunches. Using a dispersion section and an additional radiator this modulation can be used to recreate the SASE pulse envelope in a different wavelength regime (optical afterburner radiation) [1].
Using this unique feature, at the Free Electron Laser in Hamburg (FLASH) we demonstrated that the pulse duration of an XUV FEL can be obtained using standard laser diagnostics (i.e. FROG). Cross correlation with a multitude of different methods show best agreement down to several femtoseconds. [2]
Future development reaches from online pulse duration measurement to amplification and jitter-free pump probe experiments.

References

[1] E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 030701 (2010)
[2] T. Golz, Thesis: Pulse duration measurements at 4th generation X-ray light sources – Frequency Resolved Optical Gating at FLASH (2012)