% IMPORTANT: The following is UTF-8 encoded.  This means that in the presence
% of non-ASCII characters, it will not work with BibTeX 0.99 or older.
% Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or
% “biber”.

@ARTICLE{Brezinsek:858315,
      author       = {Brezinsek, S. and Pospieszczyk, A. and Sergienko, G. and
                      Dux, R. and Cavedon, M. and Faitsch, M. and Krieger, K.},
      title        = {{C}hemically assisted physical sputtering of {T}ungsten:
                      {I}dentification via the 6 Π → 6 Σ + transition of {WD}
                      in {TEXTOR} and {ASDEX} {U}pgrade plasmas},
      journal      = {Nuclear materials and energy},
      volume       = {18},
      issn         = {2352-1791},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2018-07203},
      pages        = {50 - 55},
      year         = {2019},
      abstract     = {Tungsten (W) is a preferred plasma-facing material for
                      areas of high particle and power impact in present day and
                      future fusion devices. The lifetime of W plasma-facing
                      components (PFCs) under steady-state conditions is limited
                      by erosion processes induced by energetic impinging
                      particles such as impurities (carbon C, oxygen O, nitrogen
                      N, etc.) and hydrogen isotopes above the threshold energy
                      for Physical Sputtering (PS). We discovered for the first
                      time, in addition to the bare physical sputtering process of
                      W, a second W erosion mechanism at PFCs in TEXTOR (limiter
                      surfaces) and ASDEX Upgrade (divertor target plates) during
                      deuterium plasma bombardment. The tungsten deuteride
                      molecule WD has been identified spectroscopically via the
                      transition in parallel to ordinary neutral W line emission
                      of the WI transition
                      (5d5(6S)6s 7S3 → 5d5(6S)6p 7P4) at used as measure
                      to quantify the bare PS process or, more precisely, the
                      gross erosion of W. We identified the underlying process for
                      the molecular release as Chemically Assisted Physical
                      Sputtering (CAPS) as observed also in the case of beryllium
                      or lanthanum. Measurements in TEXTOR and ASDEX Upgrade
                      showed a dependence of the WD band emission on the surface
                      temperature - connected to the deuterium content in the near
                      W surface - as well as on the flux and energy of impinging
                      energetic particles. A quantification of the released WD is
                      not yet possible due to lack of appropriate molecular data
                      for the conversion of photons into particles, but the
                      spatially resolved ratio of atomic (WI) and molecular photon
                      flux (WD) indicates that the release takes place at the same
                      time, but differently distributed along the target plates
                      and limiters reflecting the variation in the described
                      critical parameters (impinging ion flux, ion impact energy,
                      and material temperature) along the surface. The plasma
                      conditions in front of the interaction zone are in both
                      cases fully ionising with an electron temperature
                      Te > 10eV, thus, recombination into WD can be excluded.},
      cin          = {IEK-4},
      ddc          = {624},
      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:000460107500010},
      doi          = {10.1016/j.nme.2018.12.004},
      url          = {https://juser.fz-juelich.de/record/858315},
}