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@PHDTHESIS{Bellandi:474539,
      author       = {Bellandi, Andrea},
      othercontributors = {Branlard, Julien and Hillert, Wolfgang},
      title        = {{LLRF} {C}ontrol {T}echniques for the {E}uropean {XFEL}
                      {C}ontinuous {W}ave {U}pgrade},
      school       = {University of Hamburg},
      type         = {Dissertation},
      address      = {Hamburg},
      publisher    = {Universität Hamburg},
      reportid     = {PUBDB-2022-00857},
      pages        = {125},
      year         = {2021},
      note         = {A. Bellandi: thesis contains copyright-transferred
                      articles; Dissertation, University of Hamburg, 2021},
      abstract     = {In this doctoral thesis, possible solutions for
                      superconducting cavity control systems operating in the
                      Continuous Wave(CW) regime are discussed and analyzed. The
                      paper focuses on the requirements for adding a CW mode of
                      operationto European XFEL alongside the existing pulsed mode
                      of operation. The main challenge from a control system point
                      of view stems from the need to use a loaded quality factor
                      (QL) in the range of 10e7-10e8. Such a (QL) is an order of
                      magnitude greater than the actual value that is used in the
                      pulsed mode of operation. As aresult, the cavity tune is
                      more sensitive to microphonic effects. For this reason,
                      active noise compensation techniques are required in order
                      to limit the overall power consumption of the accelerating
                      system, and to increase the energy stability of the
                      accelerated beam. Another effect present in the future
                      upgrade are ponderomotive instabilities. These instabilities
                      result from the nonlinear coupling between the Lorentz
                      force-induced detuning and the cavity acceleration field.
                      These in-stabilities are then analyzed and a possible
                      compensation scheme is proposed. In order to obtain a
                      precise estimate of the cavity detuning, a real-time
                      detuning estimator has been developed. This component,
                      necessary for resonance control systems, is also used for
                      the estimation of the cavity quality factor in order to
                      realize a quench detection system. The last topic is about
                      the linearization of radio frequency amplifiers based on
                      vacuum tubes used to produce power the superconducting
                      cavities. The reason for doing a linearization of these
                      amplifiers is the improvement of the field stability and the
                      simplification of setup procedures of the RF control system.
                      For this study, Klystrons and Induction Output Tube (IOT)
                      amplifiers were used.},
      cin          = {MSK},
      cid          = {I:(DE-H253)MSK-20120731},
      pnm          = {621 - Accelerator Research and Development (POF4-621) /
                      PHGS, VH-GS-500 - PIER Helmholtz Graduate School
                      $(2015_IFV-VH-GS-500)$},
      pid          = {G:(DE-HGF)POF4-621 / $G:(DE-HGF)2015_IFV-VH-GS-500$},
      experiment   = {EXP:(DE-H253)XFEL(machine)-20150101},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:gbv:18-ediss-94297},
      url          = {https://bib-pubdb1.desy.de/record/474539},
}