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@ARTICLE{Wang:891415,
      author       = {Wang, E. and Brezinsek, S. and Sereda, S. and Buttenschön,
                      B. and Barbui, T. and Dhard, C. P. and Endler, M. and Ford,
                      O. and Flom, E. and Hammond, K. C. and Jakubowski, M. and
                      Krychowiak, M. and Kornejew, P. and König, R. and Liang, Y.
                      and Mayer, M. and Naujoks, D. and Neubauer, O. and Oelmann,
                      J. and Rasinski, M. and Winters, V. R. and Goriaev, A. and
                      Wauters, T. and Wei, Y. and Zhang, D.},
      title        = {{I}mpurity sources and fluxes in {W}7-{X}: from the
                      plasma-facing components to the edge layer},
      journal      = {Physica scripta},
      volume       = {T171},
      issn         = {1402-4896},
      address      = {Stockholm},
      publisher    = {The Royal Swedish Academy of Sciences},
      reportid     = {FZJ-2021-01500},
      pages        = {014040 -},
      year         = {2020},
      abstract     = {Wendelstein 7-X (W7-X) is a nearly full-carbon machine with
                      graphite divertors, baffles and shields in Operation Phase
                      1.2b (OP 1.2b). Divertor spectrometer measurements showed
                      that an amount of helium and oxygen impurities existed in
                      the predominately hydrogen plasma, which resulted in a high
                      carbon impurity level by enhanced physical and chemical
                      sputtering by these impurities in comparison with the pure
                      impinging proton yields. In order to improve the wall
                      conditions, especially to reduce the oxygen content,
                      boronizations were applied in OP1.2b. After the
                      boronization, an oxygen decrease by more than an order of
                      magnitude was observed. Helium disappeared in comparison
                      with OP1.2a due to reduced application of helium wall
                      conditioning after introduction of boronizations. The
                      overall radiation normalized to line integrated density was
                      reduced by a factor of six. In addition, local CH4 injection
                      was applied in the divertor in order to quantify the
                      chemical sputtering by hydrogen on divertor plates. The
                      experimentally determined effective D/XB of the A–X band
                      of CH resulting from CH4 was
                      ${\left[\tfrac{{D}}{{X}{B}}\right]}_{{{A}}^{2}{\rm{\Delta
                      }}\to {{X}}^{2}{\rm{\Pi }}}^{{\rm{C}}{{\rm{H}}}_{4}\to
                      {\rm{C}}{\rm{H}}}=16$ at Te ≈ 20 eV and ne ≈ 5 × 1018
                      m−3. It was applied to determine the hydrocarbon fluxes
                      and further to deduce the particle flux ratio ГCH4/ГH on
                      divertor plates.},
      cin          = {IEK-4},
      ddc          = {530},
      cid          = {I:(DE-Juel1)IEK-4-20101013},
      pnm          = {174 - Plasma-Wall-Interaction (POF3-174)},
      pid          = {G:(DE-HGF)POF3-174},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000520000600040},
      doi          = {10.1088/1402-4896/ab4c04},
      url          = {https://juser.fz-juelich.de/record/891415},
}