Photondiagnostics at X-Ray FEL´s

SASE FEL´s have now truly evolved into the long anticipated so called 4th generation of accelerator based X-ray light sources. A number of piloting experiments are proof that these novel X-ray sources provide radiation with the theoretically predicted unprecedented properties such as femtosecond pulse duration or Gigawatt peak power in a photon energy range extending from the soft X-ray into the hard X-ray regime. However, the success of these facilities depends strongly on the availability of suitable photon diagnostics. To be precise, due to the stochastic nature of the SASE process, properties such as pulse energy, wavelength, pulse duration and arrival time are varying from pulse to pulse and more complex experiments will crucially depend on the determination of these properties for every individual X-ray pulse. In this talk, the state of the art of currently available photon diagnostic is discussed and novel single shot techniques for the measurement of X-ray pulse duration [1] and arrival time [2] are presented.
[1] U. Fruehling, M. Wieland, M. Gensch et. al., Single-Shot THz-field-driven X-Ray streak camera, Nature Photon. 3 (2009), 528.
[2] F. Tavella, N. Stojanovic, G.A. Geloni and M. Gensch, Few-femtosecond timing at fourth-generation X-ray light sources, accepted.