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@PHDTHESIS{Heuer:405671,
      author       = {Heuer, Michael},
      othercontributors = {Lichtenberg, Gerwald and Pfeiffer, Sven},
      title        = {{I}dentification and {C}ontrol of the {L}aser-based
                      {S}ynchronization {S}ystem for the {E}uropean {X}-ray {F}ree
                      {E}lectron {L}aser},
      school       = {Technische Universität Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      publisher    = {Verlag Deutsches Elektronen-Synchrotron},
      reportid     = {PUBDB-2018-02247, DESY-THESIS-2018-018},
      series       = {DESY-THESIS},
      pages        = {164},
      year         = {2018},
      note         = {Dissertation, Technische Universität Hamburg, 2017},
      abstract     = {The European X-ray Free-Electron Laser is currently under
                      construction at theDeutsches ElektronenSynchrotron in
                      Hamburg, Germany. This linear accelerator, with a length of
                      3.4 km,will generate extremely intense and short X-ray laser
                      light pulses with a duration in the femtosecondrange and
                      wavelengths down to 0.05 nm. These laser pulses provide
                      physicists with alight source to take a closer look into
                      small structures on atomic scale.Those precise measurements
                      require timing with an error margin in the femto-second
                      rangefor most subsystems within the facility. Usually, this
                      timing signal is distributed electricallyvia coaxial cables.
                      With the new requirements in timing, this kind of
                      distribution is no longersuitable and a new laser-based
                      synchronization system is used. This system generates a
                      laserpulse train via a master laser oscillator and
                      distributes this via optical fiber to multiple endstationsin
                      the facility.The effective length of the optical path inside
                      the fiber is actively stabilizedby a link stabilizing
                      unit.This thesis analyzes this new system from a control
                      point of view. It is shown that the masterlaser oscillator
                      can be modeled by an integrator, with the H2 norm as the
                      performance criteriaand two filters corresponding to the
                      noise and disturbances of the master laser oscillator
                      itselfas well as the electrical oscillator of the facility.
                      Those influences, as well as the dynamic behaviorof the
                      master laser oscillator, are identified for a laboratory
                      setup. With these models inhand, different controllers are
                      designed and experimentally evaluated. A sufficient
                      controllerperformance can be achieved by a PI controller.
                      However, using a feedback controller witha model-based
                      optimization increase this performance, but these require a
                      high order of thecontroller, which is currently not
                      implementable given the installed hardware.The second part
                      of thiswork analyses the link stabilizing units. This is
                      achievedwith an attachedoptical fiber and a timing
                      measurement by an optical cross correlator. If a short
                      optical fiber isconnected the system can be approximated by
                      a third order system with a time delay of a fewsample.
                      Amodel is identified and used for controller design. It can
                      be shown that a performanceincrease by factor of 4.5 can be
                      achieved if an LQG controller, including a model of the
                      timedelay, is used instead of the previously used PI
                      controller. Moreover, different approaches forlong optical
                      fibers and the operation in the non-linear region of the
                      sensor are shown. Thesecould not be tested in an
                      experiment.The work closes with an analysis of the overall
                      system and gives suggestions of how to increasethe
                      performance of the individual components and of the whole
                      laser-based synchronizationsystem including the attached
                      devices. It will be shown that the optimal performance can
                      beachieved if all systems are connected to the laser-based
                      synchronization system and if the dynamicbehavior of the
                      link stabilizing unit and end-station is equal for all
                      subsystems.},
      cin          = {MSK},
      cid          = {I:(DE-H253)MSK-20120731},
      pnm          = {6G13 - XFEL (POF3-622)},
      pid          = {G:(DE-HGF)POF3-6G13},
      experiment   = {EXP:(DE-H253)XFEL-Exp-20150101},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29 / PUB:(DE-HGF)11},
      doi          = {10.3204/PUBDB-2018-02247},
      url          = {https://bib-pubdb1.desy.de/record/405671},
}