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@ARTICLE{Vinatier:586541,
      author       = {Vinatier, Thomas and Assmann, Ralph and Bruni, C. and
                      Burkart, Florian and Dinter, Hannes and Jaster-Merz, Sonja
                      Meike and Kellermeier, Max and Kuropka, Willi and Mayet,
                      Frank and Stacey, Blae},
      title        = {{C}haracterization of relativistic electron bunch duration
                      and travelling wave structure phase velocity based on
                      momentum spectra measurements on the {ARES} linac at {DESY}},
      reportid     = {PUBDB-2023-03938, arXiv:2307.12394},
      year         = {2023},
      note         = {The title has slightly changed compared to the initial
                      version submitted for approval. The content of the paper is
                      otherwise unchanged. I uploaded the version with the new
                      title and removed the others.},
      abstract     = {The ARES linac at DESY aims to generate and characterize
                      ultrashort electron bunches (fs to sub-fs duration) with
                      high momentum and arrival time stability for the purpose of
                      applications related to accelerator $R\&D,$ e.g. development
                      of advanced and compact diagnostics and accelerating
                      structures, test of new accelerator components, medical
                      applications studies, machine learning, etc. During its
                      commissioning phase, the bunch duration characterization of
                      the electron bunches generated at ARES has been performed
                      with an RF-phasing technique relying on momentum spectra
                      measurements, using only common accelerator elements (RF
                      accelerating structures and magnetic spectrometers). The
                      sensitivity of the method allowed highlighting different
                      response times for Mo and Cs2Te cathodes. The measured
                      electron bunch duration in a wide range of machine
                      parameters shows excellent agreement overall with the
                      simulation predictions, thus demonstrating a very good
                      understanding of the ARES operation on the bunch duration
                      aspect. The importance of a precise in-situ experimental
                      determination of the phase velocity of the first travelling
                      wave accelerating structure after the electron source, for
                      which we propose a simple new beam-based method precise down
                      to sub-permille variation respective to the speed of light
                      in vacuum, is emphasized for this purpose. A minimum bunch
                      duration of 20 fs rms, resolution-limited by the space
                      charge forces, is reported. This is, to the best of our
                      knowledge, around 4 times shorter than what has been
                      previously experimentally demonstrated based on RF-phasing
                      techniques with a single RF structure. The present study
                      constitutes a strong basis for future time characterization
                      down to the sub-fs level at ARES, using dedicated X-band
                      transverse deflecting structures.},
      keywords     = {velocity: phase (INSPIRE) / force: space charge (INSPIRE) /
                      electron: relativistic (INSPIRE) / linear accelerator
                      (INSPIRE) / electron: momentum spectrum (INSPIRE) /
                      electron: beam (INSPIRE) / electron: particle source
                      (INSPIRE) / stability (INSPIRE) / RF system (INSPIRE) /
                      electrode (INSPIRE) / molybdenum (INSPIRE) / cesium:
                      tellurium (INSPIRE) / DESY Lab (INSPIRE) / bunching: length
                      (INSPIRE) / numerical calculations (INSPIRE) / accelerator:
                      design (INSPIRE) / performance (INSPIRE)},
      cin          = {MPY1},
      cid          = {I:(DE-H253)MPY1-20170908},
      pnm          = {621 - Accelerator Research and Development (POF4-621) /
                      TWAC - THz Wave Accelerating Cavity for ultrafast science
                      (101046504)},
      pid          = {G:(DE-HGF)POF4-621 / G:(EU-Grant)101046504},
      experiment   = {EXP:(DE-H253)ARES-20200101},
      typ          = {PUB:(DE-HGF)25},
      eprint       = {2307.12394},
      howpublished = {arXiv:2307.12394},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2307.12394;\%\%$},
      url          = {https://bib-pubdb1.desy.de/record/586541},
}