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Operation of a free-electron laser from the extreme ultraviolet to the water window


We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 µJ for individual pulses, and the average energy per pulse reached 70 µJ. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.

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Figure 1: Peak brilliance of X-ray FELs in comparison with third-generation synchrotron-radiation light sources.
Figure 2: Production of electron bunches at FLASH.
Figure 3: Spatial profile of the FEL radiation.
Figure 4: Energy in the radiation pulse and its fluctuations.
Figure 5: EUV spectra of the fundamental (a), 3rd harmonic (b) and 5th harmonic (c) contributions to the FEL output.
Figure 6: Temporal structure of the radiation pulse for an average energy of 40 µJ, predicted by the code FAST using experimentally determined radiation properties.


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The authors are indebted to the invaluable support of the technical staff of DESY and participating groups from the TESLA Technical Collaboration.

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Correspondence to M. V. Yurkov.

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Supplementary information, figures S1-S7, tables S1-S2 (PDF 256 kb)

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Ackermann, W., Asova, G., Ayvazyan, V. et al. Operation of a free-electron laser from the extreme ultraviolet to the water window. Nature Photon 1, 336–342 (2007).

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