Author: Fenner, M.
Paper Title Page
TUPP002 Direct-Sampling Coarse Bunch Arrival Time Monitor in the Free Electron Laser FLASH Based on the Fast Digitizer Implemented in the FMC VITA 57.1 Standard 270
  • J. Zink, M.K. Czwalinna, M. Fenner, S. Jabłoński, J. Marjanovic, H. Schlarb
    DESY, Hamburg, Germany
  • F. Gerfers
    Technische Universität Berlin, Berlin, Germany
  At the free-electron lasers FLASH and European-XFEL bunch arrival times are monitored with a high-accuracy electro-optical based data acquisition system (BAM). Due to only a couple of picoseconds time measurement range of this system, large timing changes might cause the monitor to fail. To remove any ambiguity and for health status monitoring a high-speed direct-sampling FPGA mezzanine card (FMC) and an analogue RF front-end was added. The circuitry has lower precision than the electro-optical based BAM, but it can determine bunch arrival time with respect to a reference signal over a large time range, i.e. of the order of 1 ms. After restarts or larger energy changes during operation, the electron bunch arrival time may have been changed by tens or even hundreds of picoseconds, which causes that the BAM is out of its operation range and needs to be recalibrated. With the solution developed, the BAM gets the coarse bunch timing from the digitizer and adjusts its optical delay lines accordingly. This allows for finding the operation point fast and automatically. Performance data of the fast direct-sampling digitizer FMC and first measurement data from FLASH will be presented.  
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About • paper received ※ 04 September 2019       paper accepted ※ 10 September 2019       issue date ※ 10 November 2019  
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