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@ARTICLE{Mitzner:88145,
      author       = {Mitzner, R. and Sorokin, A. A. and Siemer, B. and Roling,
                      S. and Rutkowski, M. and Zacharias, H. and Neeb, M. and
                      Noll, T. and Siewert, F. and Eberhardt, W. and Richter, M.
                      and Juranic, P. and Tiedtke, K. and Feldhaus, J. and DESY},
      title        = {{D}irect autocorrelation of soft-x-ray free-electron-laser
                      pulses by time-resolved two-photon double ionization of
                      {H}e},
      journal      = {Physical review / A},
      volume       = {80},
      number       = {2},
      issn         = {1050-2947},
      address      = {College Park, Md.},
      publisher    = {APS},
      reportid     = {PHPPUBDB-10798},
      pages        = {025402},
      year         = {2009},
      note         = {© The American Physical Society},
      abstract     = {The pulse duration of soft x-ray free-electron laser (FEL)
                      radiation is directly measured by time-resolved observation
                      of doubly charged helium ions at 51.8 eV. A wave front
                      splitting autocorrelator produces two correlated FEL pulses
                      with a resolution of better than a femtosecond. In the
                      interesting intensity range from 10$_{13}$ to
                      10$_{16]$ W/cm$_2$ direct and sequential double ionization
                      contribute to the ion yield which has significant influence
                      on the correlation width, being a general feature at high
                      photon energies. Here, a duration of τL=(29±5) fs is
                      derived for the soft x-ray pulses at FLASH.},
      cin          = {HASYLAB(-2012)},
      ddc          = {530},
      cid          = {$I:(DE-H253)HASYLAB_-2012_-20130307$},
      pnm          = {FLASH Beamline BL3 (POF1-550)},
      pid          = {G:(DE-H253)POF1-BL3-20130405},
      experiment   = {EXP:(DE-H253)F-BL3-20150101},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:00},
      doi          = {10.1103/PhysRevA.80.025402},
      url          = {https://bib-pubdb1.desy.de/record/88145},
}