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Lambert, G.

Paper Title Page
MOAAU01 First Lasing in Seeding Configuration at 160 nm Using High order Harmonic Generated in gas on the FEL of the SCSS Prototype Accelerator  
 
  • 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
 
  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.  
TUPPH007 Spatial Coherence Measurement of UVSOR-II Free Electron Laser  
 
  • O. V. Chubar, M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • K. Fukui
    University of Fukui, Fukui
  • M. Hosaka
    Nagoya University, Nagoya
  • M. Katoh, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • G. Lambert
    RIKEN Spring-8, Hyogo
  • M. Labat
    CEA, Gif-sur-Yvette
 
  The well defined phase relationship of coherent radiation is wished for a large number of experiments. The advent of very small emittance electron beams allowed improvement of the transverse coherence of the undulators radiation and lead to extensive use of modern synchrotron facilities in the visible to x-ray domain. Nevertheless, Free Electron Lasers (in particular in the seeded Coherent Harmonic Generation (CHG) scheme) may offer additional capabilities such as shorter pulse duration, smaller spectral bandwidth, higher peak power and improved transverse coherence. Transverse coherence of the third Coherent Harmonic has been studied on the UVSOR-II storage ring (Japan) at 600 MeV, using a 2.5 mJ, 1 kHz, 1.2 ps Ti:Sa laser at 800 nm wavelength with the double slit method. The improvement of the transverse coherence of the FEL radiation compared to spontaneous emission is shown via the visibility of the interference pattern resulting from double slits. The experimental results are compared to analytical calculations as well as to 3D FEL and wavefront propagation simulations performed with SRW.  
TUPPH008 Beam Dynamics Studies on the UVSOR-II Free Electron Laser 236
 
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • M. Hosaka
    Nagoya University, Nagoya
  • M. Katoh, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • G. Lambert
    RIKEN Spring-8, Hyogo
  • M. Labat
    CEA, Gif-sur-Yvette
 
  In the Coherent Harmonic Generation Free Electron Laser configuration, an external laser source is seeded inside a first undulator. The interaction between the electron beam and this seed induces energy modulation of the bunch, further converted into a density modulation, producing coherent radiation in a second undulator. The energy modulation enhances the energy spread of the electron bunch, converted by the machine optics into a modification of its longitudinal distribution. In the case of a storage ring FEL, the electrons are re-circulating: the same bunch keeps interacting with the seeded laser, and relaxation of the distribution is only allowed in between two laser injections. Such specific dynamics has been studied on the CHG FEL of UVSOR-II storage ring (Japan). The electron beam stored at 600 MeV is seeded using a 2.5 mJ, 1 kHz, 1.2 ps Ti:Sa laser at 800 nm wavelength, allowing radiation at 266 nm (third harmonic). A Streak Camera is used to record the evolution of the longitudinal profiles as a function of the repetition rate and average power of the seeding laser, leading to bunch lengthening and distortion dynamical analysis. It appeared that because the heating induced by the interaction remains local, the refreshment process of the electronic distribution is modified. The experimental results are compared to simulations using SYNC.  
TUCAU02 Even Harmonic Generation on UVSOR-II Storage Ring  
 
  • M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
  • M. Hosaka
    Nagoya University, Nagoya
  • M. Katoh, A. Mochihashi, M. Shimada
    UVSOR, Okazaki
  • G. Lambert
    RIKEN Spring-8, Hyogo
  • M. Labat
    CEA, Gif-sur-Yvette
 
  In the Coherent Harmonic Generation Free Electron Laser configuration, the electrons act as a non-linear medium radiating harmonics of a seed source (e.g., a laser). In the two-step seeding scheme, the seed field forces an energy modulation on the electron bunch in a modulator, converted into a density modulation as the electron beam travels through a dispersive section. Finally, in the radiator, the microbunched electron beam can emit coherently at the fundamental and the harmonics of the seed source. In this paper, successful even harmonic generation is reported on the CHG UV-FEL of UVSOR-II storage ring (Japan) at 600 MeV, using a 2.5 mJ, 1 kHz, 1.2 ps Ti:Sa laser at 800 nm. Second and fourth harmonics were generated using planar configuration of the undulators, and second harmonic was generated in helical configuration, in addition to already observed and studied third coherent harmonic. Such preliminary results allow attractive perspectives to understand further even harmonic generation process, still discussed among the FEL community: in single pass non-guided FELs, with planar undulators even harmonics are expected to vanish on-axis, a spectral selection that could be avoided with helical undulators.  
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MOCAU03 Numerical Propagation Simulations and Coherence Analysis of SASE Wavefronts 192
 
  • M.-E. Couprie, M. Labat, G. Lambert, O. V. Chubar
    SOLEIL, Gif-sur-Yvette
  • O. Tcherbakoff
    CEA, Gif-sur-Yvette
 
  Examples of wavefront propagation simulation and coherence analysis of SASE, seeded and started-up from noise, are presented. The calculations are performed using SRW – the wave-optics computer code optimized for synchrotron radiation, and the 3D FEL simulation code GENESIS 1.3. To ensure easy inter-operation and data exchange between the two codes, GENESIS has been integrated into the "emission" part of the SRW, which is dedicated for calculation of initial wavefronts in the form ready for subsequent propagation simulations. In the examples described, after each run of GENESIS in time-dependent mode, the electric field is transformed from time to frequency domain, and the wavefront obtained this way is numerically propagated, using Fourier-optics methods implemented in the SRW, from the exit of the FEL undulator to image plane of a simple interferometer-type optical scheme. Intensity-averaged patterns, obtained after multiple cycles of the SASE (in presence of shot noise and/or a timing jitter) and the wavefront propagation calculations, allow for straightforward characterization of spatial coherence by visibility of interference fringes. SRW code can also be used for complete optimization of optical beamlines for 4th generation synchrotron radiation sources, which require accurate treatment of wave-optical phenomena in the frequency and time domains.  
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FRAAU01 Source of Radiation on ARC-EN-CIEL Proposal 505
 
  • O. V. Chubar, M. Labat, G. Lambert, O. Marcouillé, M.-E. Couprie
    SOLEIL, Gif-sur-Yvette
 
  The ARC-EN-CIEL project proposes a panoply of light sources for the scientific community. The phase 1 (220 MeV superconducting Linac, down to 30 nm) and phase 2 (1 GeV, down to 1 nm) choice to provide 30-100 fs HGHG radiation and their Non Linear Harmonics seeded with the High order Harmonics generated in Gas is further confirmed with the suceesfull demonstration experiment of such a scheme at SPA. New optimizations of the undulatros lead to in vacuum undulators of period 26 mm for the modulator, and APPLE-type radiators of period 30 mm, close to the standard SOLEIL insertion devices. New calculations have been carried out using PERSEO TD and GENESIS coupled to SRW for further propagation of the FEL wavefront to the beamlines. In addition, THz radiation from the magnets of the compression chicanes will be provided and has been calculated using SRW. ARC-EN-CIEL Phase 3 incorporates ERL loops, for hard X ray spontaneous emission above 10 keV from short period in vacuum undulators (20 mm period typically), one Soft-X ray spontaneous emission beamline using an variable polarisation undulator, and an FEL oscillator in the 10-60 nm spectral range. Recent calculations and optimisations will be presented.  
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