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- G. Lambert
LOA, Palaiseau
- M. Bougeard, B. Carré, D. Garzella, O. B. Gobert, M. Labat, H. Merdji, P. Salieres
CEA, Gif-sur-Yvette
- O. V. Chubar, M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- T. Hara, H. Kitamura, T. Shintake, M. Yabashi
RIKEN/SPring-8, Hyogo
- T. Ishikawa, K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Tanikawa
UVSOR, Okazaki
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Recently it has been proved that seeding a Free-Electron Laser with Harmonics Generated in gas can drastically improve the properties of the light emission and in particular the temporal coherence, which is quite limited in the Self-Amplified Spontaneous Emission configuration. Here, the impact of the seed level on the FEL emission has been characterized at 160 nm on the SCSS Test Accelerator. Actually, at extremely low level of HHG injection (0.5 pJ, 10 W), i.e. approximately ten times the effective noise power of the SASE emission, the FEL emission starts to be amplified and the number of spikes decrease. Then, the FEL energy per pulse begins clearly proportional to the HHG energy per pulse. More specifically for a seed power (<175 W) 230 times larger than the effective SASE noise power, the FEL spectrum exhibits a stable quasi Gaussian shape. As it is theoretically feasible to generate XUV harmonics which can be dominating with a similar factor, one can imagine High Gain Harmonic Generation configurations with only two or three stages for reaching wavelengths of a few nanometers.
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