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Allaria, E.

Paper Title Page
MOAAU03 First Lasing of the Elettra Storage-Ring Free-Electron Laser in Seeded Configuration  
 
  • E. Allaria, M. B. Danailov, B. Diviacco, E. Karantzoulis, L. Romanzin, C. Spezzani, S. Tileva, M. Trovo, G. De Ninno
    ELETTRA, Basovizza, Trieste
  • M. Coreno
    CNR - IMIP, Trieste
  • F. Curbis
    Università degli Studi di Trieste, Trieste
 
  We report the first lasing of the Elettra storage-ring free-electron laser operated in “single-pass” seeded configuration. The external seed was provided by a Ti:Sa laser tuned at 780 and 390 nm, with adjustable repetition rate (10 Hz – 1kHz) and pulse duration (100 fs or 1 ps). We have obtained intense coherent radiation in the spectral range between 130 and 260 nm. Harmonic pulses are characterized by high peak power (orders of magnitudes above spontaneous radiation) and very good stability (fluctuations of few percent). The signal is transform limited. The Elettra optical klystron is made of independent APPLE-type undulators. This allows complete freedom in the choice of light polarization. Presently, all the above features make the Elettra free-electron laser in seeded configuration a unique light source, which is attractive for several user experiments.  
MOPPH015 Limit for Harmonic Conversion in a Single Cascade of Coherent Harmonic Generation 50
 
  • G. De Ninno, E. Allaria
    ELETTRA, Basovizza, Trieste
 
  Harmonic generation is a reliable method for producing coherent high-brightness photon pulses from relativistic electron bunches. The standard process leading to Coherent Harmonic Generation (CHG) is initiated by a powerful seed laser. As a consequence, reaching short wavelengths generally requires a high order frequency conversion. For that reason some of the projects which are presently under development for coherent VUV and soft-Xray emission are based on a series of two or more consecutive "cascades". In these setups, the radiation produced into one CHG stage is used as a seed in a following CHG cascade. The required number of cascades is related to the maximum harmonic conversion which can be obtained in single stages. In this paper the mechanism underlying the CHG, i.e. the bunching creation into the modulator, is studied in detail and the physical limits for the single-stage CHG are investigated. The identification of the limiting parameters may allow the implementation of new methods for enhancing the conversion efficiency. One of these methods, which relies on a simple modification of the standard CHG scheme, has been recently proposed* and shown to be able to significantly improve the system performance. Results are confirmed by numerical simulations using the codes Ginger and Genesis. Expected impact on some of the existing projects for CHG is also presented.

* E. Allaria, G. De Ninno, Phys. Rev. Lett., to be published.

 
TUCAU03 Seeded Harmonic Generation with the Elettra Storage-Ring Free Electron Laser  
 
  • E. Allaria, M. B. Danailov, G. De Ninno, B. Diviacco, E. Karantzoulis, C. Spezzani, S. Tileva, M. Trovo, F. Curbis
    ELETTRA, Basovizza, Trieste
  • M. Coreno
    CNR - IMIP, Trieste
 
  We have recently demonstrated that the Elettra storage-ring free-electron laser is well suited for producing intense VUV harmonic radiation in seeded "single-pass" configuration. After reviewing the experimental setup, we present here the temporal and spectral characterization of the harmonic pulse with respect to several adjustable parameters, such as the seed power, repetition rate (10 Hz ± 1 kHz) and pulse duration, the seed pulse-electron bunch temporal detuning and the strength of the dispersive section between undulators. Measured peak power in the working wavelength range (i.e., 260-130 nm for the reported experiments) is several orders of magnitude above spontaneous synchrotron radiation. We also show that measurements are in very good agreement with 3D numerical simulations. The obtained results make the Elettra storage-ring free-electron laser in seeded "single-pass" configuration an ideal test facility for next generation linac-based FELs and, at the same time, a ready-to-use light source for user experiments.