| Paper |
Title |
Page |
| MOPPH054 |
Spectral Characteristics of the Seeded FEL Using Higher Harmonic Generation in a Gas at the SCSS Test Accelerator
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106 |
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- T. Tanikawa
Sokendai, Okazaki, Aichi
- B. Carré, D. Garzella, M. Labat
CEA, Gif-sur-Yvette
- M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- T. Hara, T. Ishikawa, H. Kitamura, T. Shintake, T. Tanaka, M. Yabashi
RIKEN/SPring-8, Hyogo
- M. Katoh
UVSOR, Okazaki
- G. Lambert
LOA, Palaiseau
- K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
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Seeding a FEL with high order harmonic generation (HHG) from a Xe gas cell at the SCSS test accelerator was achieved at a wavelength of 160 nm (the 5th harmonic of a Ti: Sa laser) in December 2006. After the improvement of the accelerator performance in 2007, we performed detailed studies of the spectral characteristics of the seeded FEL. Compared to the spiky spectrum of SASE, the seeded FEL can produce a quasi-Gaussian spectrum with a single peak. In addition, the lasing wavelength is fixed at the wavelength of the seed, even if the undulator K-parameter is shifted in a certain range. Therefore, the spectral stability becomes much better than SASE against the fluctuation of undulator fields or beam energy. In the recent experiments, we observed that the bandwidth of the amplified seed became narrower than that of the original seed light itself. It seems to be stretched the longitudinal coherent length in the FEL interaction. In the presentation, we will report the spectral characteristics of the seeded FEL.
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| TUBAU01 |
VUV Seeded FEL Experiment at the SCSS Test Accelerator
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207 |
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- T. Hara, T. Ishikawa, H. Kitamura, T. Ohshima, T. Shintake, T. Tanaka, M. Yabashi
RIKEN/SPring-8, Hyogo
- B. Carré, D. Garzella
CEA, Gif-sur-Yvette
- M.-E. Couprie, M. Labat
SOLEIL, Gif-sur-Yvette
- G. Lambert
LOA, Palaiseau
- K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Tanikawa
Sokendai, Okazaki, Aichi
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Short wavelength seeded FEL has been demonstrated at the SCSS test accelerator using high order harmonics generated in gas of a Ti:Sa laser as an external seed source. After the improvement of the accelerator stability and undulator magnetic errors in 2007, the FEL gain was drastically increased and detailed measurements have been carried out on the spectral characteristics and seeding power level of the seeded FEL. Although the wavelength of the seed is 160 nm for the moment, we have succeeded to observe up to 7th nonlinear harmonics (23 nm) of the 160 nm FEL fundamental including both odd and even harmonics. It leads to the development of a short wavelength seeded FEL. Currently we are working on the modification of the seeding system in order to reach a 50-60 nm range using high order harmonics in the plateau region. By combining a short wavelength seed with nonlinear harmonics, a seeded FEL below 10 nm becomes feasible. In the conference, we will present the recent results of the experiments together with the technical issues of the seeded FEL, such as temporal jitter between laser pulses and electron bunches.
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| TUPPH080 |
FEL Emissions at 160 nm in Seeded Configuration on the SCSS Test Accelerator
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429 |
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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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