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@ARTICLE{Zhao:878798,
      author       = {Zhao, Dongye and Yi, R. and Oelmann, J. and Brezinsek, S.
                      and Rasinski, M. and Gao, Y. and Mayer, M. and Dhard, C. P.
                      and Krause, M.},
      title        = {{E}x situ analysis of {W}7-{X} divertor plasma-facing
                      components by picosecond laser diagnostics},
      journal      = {Physica scripta},
      volume       = {T171},
      issn         = {1402-4896},
      address      = {Stockholm},
      publisher    = {The Royal Swedish Academy of Sciences},
      reportid     = {FZJ-2020-03051},
      pages        = {014018 -},
      year         = {2020},
      abstract     = {A key question of long-pulse operation in the stellarator
                      Wendelstein 7-X (W7-X) is the net erosion of plasma-facing
                      components (PFCs), which determines W7-X PFC lifetimes as
                      well as the impact on the impurity influx to the plasma. In
                      order to judge the erosion and deposition balance at the
                      passively cooled graphite divertor, a set of exchangeable
                      graphite tiles with marker layer stripes consisting of
                      5–10 μm C deposited on a 200 nm thick Mo interlayer were
                      installed as an integral part of the divertor surface and
                      removed at the end of the first operational phase for
                      post-operational analysis. Laser-induced breakdown
                      spectroscopy (LIBS) combined with laser-induced
                      ablation-quadrupole mass spectrometry (LIA-QMS) were used
                      for further analysis. The LIBS results show that the
                      erosion-dominated regions are close to the location of the
                      strike lines in standard magnetic configuration of W7-X
                      optimised for the island divertor concept. Almost the
                      complete C/Mo marker layer is eroded in these regions,
                      providing an average erosion rate of 4.3 nm s−1 in the
                      2481 s plasma seconds of the campaign. In parallel, only a
                      little deposition at the edge of the divertor tiles, where
                      Mo is observed on the bulk graphite material was found.
                      Furthermore, LIA-QMS showed a high hydrogen content on
                      uncoated bulk graphite areas, while a lower hydrogen
                      concentration was detected in the erosion-dominated zone,
                      caused by the high surface temperature at the strike line
                      during plasma operation.},
      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:000520000600018},
      doi          = {10.1088/1402-4896/ab3ee1},
      url          = {https://juser.fz-juelich.de/record/878798},
}