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Ludwig, F.

Paper Title Page
MOPAN017 Noise and drift characterization of direct laser to RF conversion scheme for the laser based synchronization system for FLASH at DESY 182
  • F. Ludwig, B. Lorbeer, H. Schlarb, A. Winter
    DESY, Hamburg
  Funding: This contribution is funded by the EUROFEL project.

The next generation of FEL's (Free Electron Lasers) require a long and short term stable synchronisation of RF reference signals with an accuracy of 10 fs. For that an optical synchronisation system is developed for FLASH at DESY, that is based on optical pulse train which carry the timing information encoded in its precise repetition rate. The optical pulse train has to be converted into an RF signal to provide a local reference for calibration and operation of RF based devices. The drift and jitter performance of the optical to RF converter influences directly the phase stability of the accelerator. Three different methods for optical to RF converters, namely the direct photodiode detection, injection locking and a sagnac loop interferometer are currently under investigation. In this paper we concentrate on the jitter and drift performance of the direct photodiode conversion and show its limitations from measurement results.

MOPAN019 Performance of the New Master Oscillator and Phase Reference System at FLASH 188
  • S. Simrock, M. Felber, M. Hoffmann, B. Lorbeer, F. Ludwig, H. C. Weddig
    DESY, Hamburg
  • K. C. Czuba
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  The master oscillator and phase reference system at FLASH must provide several rf reference frequencies to widely spread locations with low phase noise and small long term phase drifts. The phase noise requirements of the 1300 MHz reference is of the order of 0.1 deg. while short and medium term phase stability is of of the order of 0.1 deg. and 1 deg. respectively. The frequency distribution system employs a temperature stabilized coaxial line for rf power distribution and a fiber optic system for the monitoring of phase drifts. Presented are the the concept, design and performance measured in the accelerator environment.  
WEPMN011 Multichannel Downconverter for the Next Generation RF Field Control for VUV- and X-Ray Free Electron Lasers 2071
  • M. Hoffmann, F. Ludwig, H. Schlarb, S. Simrock
    DESY, Hamburg
  Funding: We acknowledge financial support by DESY Hamburg and the EUROFEL project.

For pump- and probe experiments at VUV- and X-ray free-electron lasers the stability of the electron beam and timing reference must be guaranteed in phase for the injector and bunch compression section within a resolution of 0.01 degree (rms) and in amplitude within 1 10-4 (rms). The performance of the field detection and regulation of the acceleration RF critically influences the phase and amplitude stability. For the RF field control, a multichannel RF downconverter is used to detect the field vectors and control the vectorsum of 32 cavities. In this paper a new design of an 8 channel downconverter is presented. The downconverter frontend consists of a passive rf double balanced mixer input stage, intermediate filters and an integrated 16bit analog-to-digital converter (ADC). The design includes a digital motherboard for data preprocessing and communication with the controller. In addition we characterize the downconverter performance in amplitude and phase jitter, temperature drifts and channel crosstalk in laboratory environment as well as for accelerator operation.