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Few-femtosecond timing at fourth-generation X-ray light sources

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Fourth-generation X-ray light sources are being developed to deliver laser-like X-ray pulses at intensities and/or repetition rates that are beyond the reach of table-top devices. An important class of experiments at these new facilities comprises pump–probe experiments, which are designed to investigate chemical reactions and processes occurring on the molecular or even atomic level, and on the timescale of a few femtoseconds. Good progress has been made towards the generation of ultrashort X-ray pulses (for example, at FLASH1 or LCLS2), but experiments suffer from the intrinsic timing jitter between the X-ray pulses and external laser sources3. In this Letter, we present a new approach that provides few-femtosecond temporal resolution. Our method uses coherent terahertz radiation generated at the end of the X-ray undulator by the same electron bunch that emits the X-ray pulse. It can therefore be applied at any advanced light source working with ultrashort electron bunches and undulators.

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Figure 1: Calculated radial and temporal distribution of the terahertz edge radiation pulse generated from the X-ray undulator and the electron beam dump for a 580 MeV electron beam energy.
Figure 2: Electric field of the edge radiation pulse.
Figure 3
Figure 4: Single-shot electric field profiles.

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  • 13 February 2011

    In the Acknowledgements section of this Letter originally published online, the grant number was incorrect. This has been corrected for all versions of the Letter.


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The authors acknowledge technical support from B. Polzin and fruitful discussion with B. Faatz, E. Saldin, E. Schneidmiller and M.V. Yurkov (Deutsches Elektronen Synchrotron). We are deeply indebted to A.L. Cavalieri (Max Planck Research Group for Structural Dynamics) and A. Azima (University of Hamburg) for sharing insights. This work was supported by the German Ministry of Education and Research (BMBF; grant no. 05K10CHC).

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M.G., N.S. and F.T. contributed equally to the work. G.G. performed calculation of the terahertz electric fields.

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Correspondence to F. Tavella, N. Stojanovic or M. Gensch.

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The authors declare no competing financial interests.

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Tavella, F., Stojanovic, N., Geloni, G. et al. Few-femtosecond timing at fourth-generation X-ray light sources. Nature Photon 5, 162–165 (2011).

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