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@MASTERSTHESIS{Genthe:610991,
      author       = {Genthe, Erik},
      othercontributors = {Burmeister, Carsten and Schlarb, Holger},
      title        = {{I}mpact of ocean-generated microseism on the {E}uropean
                      {X}-ray {F}ree {E}lectron {L}aser},
      school       = {Fachhochschule Wedel},
      type         = {Masterarbeit},
      reportid     = {PUBDB-2024-04783},
      pages        = {51},
      year         = {2024},
      note         = {Masterarbeit, Fachhochschule Wedel, 2024},
      abstract     = {In this thesis, it is shown that ocean-generated microseism
                      significantly impacts the synchronisation performance of the
                      European X-ray free-electron laser (XFEL), which is based on
                      a high-energy linear accelerator. Using superconducting
                      technology, it generates hard X-ray pulses at megahertz
                      frequencies. Arrival time stability refers to the precision
                      and consistency of the timing of the X-ray pulses, ensuring
                      that they arrive at the target with minimal variation in
                      their temporal alignment. Ocean-generated microseism is
                      low-frequency seismic noise caused by the interaction of
                      ocean waves with the seabed. Distributed acoustic sensing
                      (DAS) is a technology that turns optical fibres into a
                      sensor array for monitoring acoustic signals along their
                      length. By measuring tiny changes in light reflection caused
                      by acoustic disturbances, DAS can provide real-time
                      information about vibrations over long distances.Notably,
                      the bunch arrival time monitors (BAM) show noise between
                      0.05 Hz and 0.5 Hz, which has a significant impact on the
                      arrival time stability at European XFEL. The impact can be
                      more than 25 fs peak-to-peak. By correlating European XFEL
                      bunch arrival time data with seismic DAS measurements, it is
                      shown that the noise is of seismic origin. Next, both
                      primary and secondary ocean-generated microseism were
                      identified using seismometers and a numerical ocean wave
                      model. Whereas secondary microseism has a strong impact on
                      the bunch arrival time, primary microseism has no notable
                      effect. This is attributed not only to the smaller
                      amplitudes of secondary microseism but also to the fact that
                      primary microseism has a higher Love wave to Rayleigh wave
                      ratio. The effect on the bunch arrival time is caused by
                      Rayleigh waves, while Love waves have a negligible influence
                      on the bunch arrival time. In the presented cases, the noise
                      originates from the North Atlantic and/or the North Sea. The
                      amplitude of the noise depends on the weather conditions in
                      the North Sea and the North Atlantic and is generally much
                      stronger in winter. In conclusion, this work shows that
                      ocean-generated microseism is a significant bottleneck that
                      must be addressed to achieve femtosecond bunch arrival time
                      stability.},
      cin          = {MSK},
      cid          = {I:(DE-H253)MSK-20120731},
      pnm          = {621 - Accelerator Research and Development (POF4-621) /
                      6G13 - Accelerator of European XFEL (POF4-6G13)},
      pid          = {G:(DE-HGF)POF4-621 / G:(DE-HGF)POF4-6G13},
      experiment   = {EXP:(DE-H253)XFEL(machine)-20150101},
      typ          = {PUB:(DE-HGF)19},
      doi          = {10.3204/PUBDB-2024-04783},
      url          = {https://bib-pubdb1.desy.de/record/610991},
}