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    Item type:Publication, Access status: with files ,
    Impact of seismic activities on the optical synchronization system of the European X-ray free-electron laser
    (Cambridge University Press (CUP), 2025-03-05)
    Grünhagen, Arne
    ;
    Schütte, Maximilian
    ;
    Lamb, Thorsten
    ;
    Schulz, Sebastian
    ;
    Eichler, Annika
    This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser. We analyze the controller I/O data of phase-locked-loops in length-stabilized links, focusing on the response to earthquakes, ocean-generated microseism and civilization noise. By comparing the controller data with external data, we were able to identify disturbances and their effects on the control signals. Our results show that seismic events influence the stability of the phase-locked loops. Even earthquakes that are approximately 5000 km away cause remarkable fluctuations in the in-loop control signals. Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence. The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization, such as road traffic or major events like concerts or sport events. The phase-locked loops manages to eliminate more than 99 % of the existing interference.
    Publicationtype: Journal Article
      23  40
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    Item type:Publication, Access status: with files ,
    Laser-to-RF phase detection with femtosecond precision for remote reference phase stabilization in particle accelerators
    (Verlag Deutsches Elektronen Synchrotron, 2017)
    Lamb, Thorsten
    ;
    Brinkmeyer, Ernst
    The invention of a femtosecond stable Laser-to-RF phase detector allows to measure with femtosecond precision the relative phase between a phase stable optical reference and an RF signal. Thereby one can stabilize RF reference signals in modern FELs on a femtosecond scale. A pulsed optical synchronization system is used to deliver the required optical reference signals. The L2RF phase detector is based on an integrated Mach-Zehnder modulator (MZM) in which the phase error between both signals is encoded in an amplitude modulation of the optical pulse train. Different configurations for different operation scenarios have been evaluated. A full mathematical representation has been derived. The impact of multiple error sources has been investigated. Error sources of the measurement setup have been identified and eliminated. The femtosecond performance has been verified with two different prototypes. The achieved stability of 3.6fs over 12h is currently unmatched.
    Publicationtype: Doctoral Thesis
      607  1165