FROA :: Soft and Hard X-Ray FELs: Femtosecond Pulses, Reduced Line Width, Synchronization

Date/Time: 26-Aug-05 :: 08:30—10:15
Chair: E. Jaeschke, BESSY GmbH, Berlin

Paper Title Page
FROA001 What to Do with Femtosecond Pulses?
 
  • P.H. Bucksbaum
    Michigan University, Ann Arbor, Michigan
 
 

No abstract received.

 
   
FROA002 Synchronization of Femtosecond Pulses 676
 
  • A. Winter, H. Schlarb
    DESY, Hamburg
  • dc. Cheever, J. Chen, F.O. Ilday, F.X. Kaertner, J. Kim, D. Wang, T. Zwart
    MIT, Middleton, Massachusetts
  • P. Schmuser
    Uni HH, Hamburg
 
 

X-ray pulses with a pulse duration of down to 30 fs FWHM or even sub-fs are desired for various experiments planned at next generation free electron lasers, such as the European XFEL. A synchronization of the probe system in the experimental area to the x-ray pulses with stability on the order of the pulse width is highly desirable for these experiments. This requirement translates to distributing an ultra-stable timing signal to various subsystems of the machine and the experimental area to provide synchronization at the fs level over distances of up to several kilometers. A few years ago, a timing and synchronization system providing stability to the fs level was unthinkable. Recent advances in the field of ultra-short pulse lasers have made optical synchronization systems with such a precision feasible. This talk will focus on an optical approach using a train of ultra-short pulses distributed through optical fiber links. The timing information is contained in the precise repetition rate. First results of such a system operating in an accelerator environment will be reported.

 
   
FROA003 FERMI @ Elettra: A Seeded Harmonic Cascade FEL for EUV and Soft X-Rays 682
 
  • C.J. Bocchetta, D. Bulfone, P. Craievich, G. D'Auria, M.B. Danailov, G. De Ninno, S. Di Mitri, B. Diviacco, M. Ferianis, A. Gomezel, F. Iazzourene, E. Karantzoulis, G. Penco, M. Trovo
    ELETTRA, Basovizza, Trieste
  • J.N. Corlett, W.M. Fawley, S.M. Lidia, G. Penn, A. Ratti, J.W.  Staples, R.B. Wilcox, A. Zholents
    LBNL, Berkeley, California
  • M. Cornacchia, P. Emma, Z. Huang, J. Wu
    SLAC, Menlo Park, California
  • W. Graves, F.O. Ilday, F.X. Kaertner, D. Wang, T. Zwart
    MIT, Middleton, Massachusetts
  • F. Parmigiani
    Universita Cattolica-Brescia, Brescia
 
 

We describe the machine layout and major performance parameters for the FERMI FEL project funded for construction at Sincrotrone Trieste, Italy. The project will be the first user facility based on seeded harmonic cascade FELs, providing controlled, high peak-power pulses. With a high-brightness rf photocathode gun, and using the existing 1.2 GeV S-band linac, the facility will provide tunable output over a range from ~100 nm to ~10 nm, with pulse duration from 40 fs to ~ 1ps, and with fully variable output polarization. Initially, two FEL cascades are planned; a single-stage harmonic generation to operate > 40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelength. The output is spatially and temporally coherent, with peak power in the GW range. Lasers provide modulation to the electron beam, as well as driving the photocathode and other systems, and the facility will integrate laser systems with the accelerator infrastructure, including a state-of-the-art optical timing system providing synchronization of rf signals, lasers, and x-ray pulses. Major systems and overall facility layout are described, and key performance parameters summarized.

 
   
FROA004 Fiber Transmission Stabilization by Optical Heterodyning Techniques and Synchronization of Mode-Locked Lasers Using Two Spectral Lines 686
 
  • J.W.  Staples, R.B. Wilcox
    LBNL, Berkeley, California
 
 

Funding: This work supported by the US Department of Energy under contract No. DE-AC03-76SF00098

Stabilization of the transit time through a glass fiber using an optical heterodyne technique promises to provide jitter reduction down to the few femtosecond level using inexpensive commodity hardware. An acousto-optical frequency shifter provides the optical frequency offset that is used to downconvert phase shifts at optical frequency to equivalent phase shifts at radio frequency which are used to close a phase-lock loop driving a piezoelectric phase shifter. Using the stabilized fiber transmission medium, two spectral lines of a mode locked laser lock two low-power CW lasers which are transmitted to a receiver which phase locks the same spectral lines of a second mode-locked laser to the first. The optical transmission system operates at low power and is linear, providing excellent signal-to-noise ratio and allows many signals to be transmitted without mutual interference. Experimental results will be presented.

 
   
FROA005 Optical Laser Synchronized to the DESY VUV-FEL for Two-Color Pump-Probe Experiments 690
 
  • I. Will
    MBI, Berlin
  • S. Düsterer, J. Feldhaus, E. Plönjes, H. Redlin
    DESY, Hamburg
 
 

Funding: This work was funded by the European Commission under Contract no. HPRI-CT-1999-50009

The VUV-FEL at DESY provides ultra-short pulses with pulse durations below 50 fs. To explore a wider field of time resolved experiments a complex laser system has been installed delivering 150 fs pulses at a wavelength of 800 nm with 50 μJ pulse energy at 1MHz repetition rate during the FEL burst (of 800 μs). In order to perform two color pump-probe experiments the laser has to be synchronized to the FEL. To ensure precise and reliable synchronized operation of the laser, various diagnostic experiments have been developed. Concepts as well as first results of the synchronization will be shown.