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Schulz, S.

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WEOCMH02 Recent Developments of the Beam Arrival Time Monitor with Femtosecond Resolution at FLASH 2405
 
  • M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt, J. Zemella
    DESY, Hamburg
  • F. Löhl
    CLASSE, Ithaca, New York
  • S. Schulz, L.-G. Wißmann
    Uni HH, Hamburg
 
 

At FLASH an optical synchronisation system with femtosecond stability is now being installed and commissioned. The system is based on pulses from a passively modelocked fibre laser which are distributed in length-stabilised fibres to various end-stations. Several modifications and improvements with respect to the original layout, especially concerning permanent operation and reliability, are already incorporated at this stage. The electron bunch arrival-time monitors (BAM), based on electro-optical modulation, are an integral part of the system. Built on the experiences with first prototypes, the most recent version of the BAM, installed prior to the first bunch compressor, includes essential changes affecting the optical layout, the mechanical and thermal stability as well as the electronics for read-out and controls. The revised BAM showed improved performance and will be complemented by a second congenerous BAM after the first bunch compressor during the present FLASH upgrade. The experiences with installation as well as the scope of improvements as to simplification and long-term stability will be presented.

 

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Slides

 
WEPEB076 Precision Synchronization of the FLASH Photoinjector Laser 2875
 
  • S. Schulz, L.-G. Wißmann
    Uni HH, Hamburg
  • V. R. Arsov
    PSI, Villigen
  • M.K. Bock, M. Felber, P. Gessler, K.E. Hacker, F. Ludwig, H. Schlarb, B. Schmidt, J. Zemella
    DESY, Hamburg
 
 

After its upgrade, the free-electron laser in Hamburg (FLASH) will start operating with an exchanged RF-gun driven by an improved photoinjector laser. Since the SASE FEL process is very sensitive to the RF gun phase it is highly desirable to implement phase stabilization feedback, which, in turn, requires an arrival-time stabilization of the photoinjector laser pulses. In this paper we report on the synchronization of the photoinjector laser system to the optical timing reference using an optical cross-correlation scheme. This enables not only the measurement of the timing jitter, but also the stabilization using adaptive feed-forward algorithms acting on an EOM incorporated in the laser's pulse train oscillator. First results from the commissioning and future plans for a feedback system are discussed.