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| MOAAU01 |
First Lasing in Seeding Configuration at 160 nm Using High order Harmonic Generated in gas on the FEL of the SCSS Prototype Accelerator
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- B. Carré, D. Garzella, O. B. Gobert, M. Labat, H. Merdji, P. Salieres, G. Lambert
CEA, Gif-sur-Yvette
- O. V. Chubar, M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- T. Hara, H. Kitamura, T. Shintake, K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- S. Inoue
JASRI/SPring-8, Hyogo-ken
- T. Tanikawa
University of Hyogo, Hyogo
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Coherent radiation has been observed at 160 nm, 54 nm and 32 nm (respectively fundamental, 3rd and 5th non linear harmonics) by seeding the 5th harmonic of a Ti: Sa laser (800 nm, 50 mJ, 10 Hz, 100 fs) generated in a Xe gas cell inside the FEL of the SCSS (SPring-8 Compact Sase Source, Japan) Prototype Accelerator. In this configuration, the external source is focalized at the beginning of the first in-vacuum undulator section (300 periods, 15 mm of period) in order to interact properly with the electron beam (150 MeV, 0.3 nC, 10 Hz, 1 ps). The details of the experimental set-up will be given. With one undulator section, high amplification levels and shortening of the spectral width compared to the spontaneous emission have been measured. When adding the second undulator section, saturated signal is apparently observed. The measurements are then compared with time dependant simulations using PERSEO and GENESIS included in SRW. Finally, perspectives offered by seeding an FEL with High order Harmonics Generated in gas, following this first experimental demonstration, will be derived for 4th generation light sources in the soft X-ray range.
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| WEPPH001 |
Femtosecond CPA-based Laser Research & Development Program for Photoinjectors
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- D. Garzella, S. Grabielle, J-F. Hergott, Ph. Hollander, D. Jourdain, F. Lepetit, M. Perdrix, O. Tcherbakoff, O. B. Gobert
CEA, Gif-sur-Yvette
- T. Oksenhendler
FASTLITE, Palaiseau
- G. D. Rovera
LNE-SYRTE, Paris
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High Brightness, electron Linac-based light sources call for synergy with conventional high energy laser sources. Indeed, photoinjectors R&D needs lasers R&D. The Ti:S lasers based on Chirped Pulse Amplification (CPA) techniques can supply the requested light features for operating with such accelerator systems, provided that one can shape and control the laser pulses in the temporal and spatial domain. In the EUROFEL European program framework, the investigations performed by the LUCA/PLFA team at the Saclay Laser Interaction Center are twofold : - Temporal and spatial shaping of fs UV laser pulses. Temporal beam shaping is performed through an amplitude and phase modulation in the pulse spectral domain by means of an active programmable system. Transverse pulse shaping is achieved with a passive optical system based on aspheric optics. A combination of both techniques allows one to obtain "beer can" shaped photoelectron bunches easily. -Investigations in laser/LINAC synchronization and timing distribution. Optical experimental techniques are used to measure the drift and the jitter at the output laser system whose oscillator repetition rate is locked on a Rb atomic clock. In the present paper the major numerical studies and experimental results are presented. Further considerations on the benefits and the limits brought by these experimental techniques will be discussed.
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| WEPPH002 |
Longitudinal and Spatial shaping of UltraViolet Femtosecond laser pulses: Theoretical Investigations and Experimental Results
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- D. Garzella, S. Grabielle, J-F. Hergott, Ph. Hollander, D. Jourdain, F. Lepetit, M. Perdrix, O. Tcherbakoff, O. B. Gobert
CEA, Gif-sur-Yvette
- T. Oksenhendler
FASTLITE, Palaiseau
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The search for minimized emittance high charge electron bunches calls for increased efforts in controlling the temporal and spatial features of photoinjector drive lasers. In the EUROFEL framework, the LUCA/PLFA team in Saclay (SLIC) is investigating the longitudinal and transverse shaping of ultrashort laser pulses. The main goal is to obtain properly shaped UV (@266 nm) ps laser pulses. Temporal pulse shaping is performed through amplitude and phase modulation in the spectral domain with an acousto-optic programmable dispersive filter (Dazzler). Square and parabolic shapes are achieved either by modulating an IR laser pulse (@800 nm) before UV up-conversion, or by a direct manipulation of the UV pulse. Analogies and differences between the two procedures are here underlined through theoretical and experimental studies. Transverse shaping is obtained by using a passive optical system based on aspheric optics, leading to a homogeneous flat-top transverse distribution. The major results on a UV pulse are shown. Moreover, preliminary experimental studies, introducing the use of a deformable mirror and the effects of spatial phase modulation on the laser pulse are also presented here, together with a theoretical analysis. Combined longitudinal and transverse shaping allows us to obtain "beer can" shaped laser pulses easily, and thus photoelectron bunches of the same shape.
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| WEPPH045 |
Femtosecond-level Timing Instabilities on CPA-based Laser Systems
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- D. Garzella, O. B. Gobert, J-F. Hergott, Ph. Hollander, D. Jourdain, F. Lepetit, M. Perdrix, O. Tcherbakoff
CEA, Gif-sur-Yvette
- G. D. Rovera
LNE-SYRTE, Paris
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An essential feature for operating accelerator-based light sources is the Timing and Synchronization system. This is necessary in photoelectron bunches generation, in order to synchronize the drive laser with the RF of the accelerating cavity, or in the seeding of an external laser in an undulator. A unique Timing Standard is also required by the end-users for setting up time resolved pump-probe experiments. These various needs call for sub-ps synchronization level. The LUCA/PLFA team at the Saclay Laser Interaction Center (SLIC) developed an experimental setup to lock the repetition rate of the oscillator of the CPA-based laser system on a Rb atomic clock. An analysis of the temporal characteristics of the system without this stabilization is presented, showing the influence of the environmental parameters (temperature, atmospheric pressure and humidity) on the oscillator rate. The results obtained with the stabilization system on, are then presented and analyzed using classical methods (Allan variance and phase power spectral density). In order to investigate experimentally the temporal jitter and drift which can appear inside the laser system, a Fourier Transform Spectral Interferometry experiment has been set up. This experiment should give us an accuracy of tens of fs. Detailed results and analysis will be presented.
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