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@INPROCEEDINGS{Kreter:874453,
      author       = {Kreter, A. and Nishijima, D. and Doerner, R. P. and
                      Freisinger, M. and Linsmeier, Ch. and Martynova, Y. and
                      Möller, S. and Rasinski, M. and Reinhart, M. and Terra, A.
                      and Torikai, Y. and Unterberg, B.},
      title        = {{I}nfluence of plasma impurities on the fuel retention in
                      tungsten},
      reportid     = {FZJ-2020-01454},
      year         = {2019},
      abstract     = {Influence of plasma impurities on the fuel retention in
                      tungstenA. Kreter1, D. Nishijima2, R.P. Doerner2, M.
                      Freisinger1, Ch. Linsmeier1, Y. Martynova1, S. Möller1, M.
                      Rasinski1, M. Reinhart1, A. Terra1, Y. Torikai3 and B.
                      Unterberg11Forschungszentrum Jülich GmbH, Institut für
                      Energie- und Klimaforschung - Plasmaphysik, Partner of the
                      Trilateral Euregio Cluster (TEC), 52425 Jülich,
                      Germany2University of California San Diego, 9500 Gilman Dr.,
                      La Jolla, CA 92093-0417, USA3Faculty of Science, Ibaraki
                      University, Mito, Ibaraki 310-8512, JapanThe retention of
                      radioactive tritium in the reactor wall is a safety issue
                      and should be kept to a minimum. We investigated the
                      influence of helium, argon, neon and nitrogen as plasma
                      impurities on the deuterium retention in tungsten in the
                      linear plasma devices PSI-2 and PISCES-A. Following mixed
                      plasmas were produced: pure D, D+He, D+Ar, D+Ne, D+N and
                      D+He+Ar, with impurity fractions between $3\%$ and $10\%.$
                      The exposure conditions were as follows: incident ion flux
                      of ~1021 to 1022 m-2s-1, incident ion fluence of 1×1025 to
                      11026 m-2, sample temperatures of 500 and 770 K. The
                      incident ion energy was 70 eV, above the tungsten sputtering
                      threshold for argon and nitrogen, but below it for deuterium
                      and helium. For neon, in addition, it was varied between 20
                      and 70 eV, below and above the tungsten sputtering
                      threshold, respectively. The admixture of helium reduced the
                      deuterium retention by a factor of 3-100, with a stronger
                      reduction of a higher sample temperature. In the D+He+Ar
                      case the retention was similar as for pure D. Argon
                      sputtered the near-surface helium nanobubble layer and thus
                      overrode the effect of helium. The effect of neon is
                      sensitive to the incident ion energy. Addition of nitrogen
                      increased the deuterium retention by a factor of ~10 and
                      ~100 for 500 and 770 K, respectively. In general, the effect
                      of impurities on the deuterium retention appears to be
                      sensitive to the properties of the affected near-surface
                      layer of tungsten. Admixed species, i.e. helium, can form a
                      layer with open porosity, which serves as an additional
                      release channel for deuterium thus decreasing the retention.
                      However, if the process is dominated by sputtering, as for
                      argon, such a layer cannot be formed. The nitrogen enriched
                      layer, in contrast, serves as a desorption barrier for
                      deuterium increasing the retention.},
      month         = {Oct},
      date          = {2019-10-22},
      organization  = {7th International Workshop on Plasma
                       Material Interaction Facilities for
                       Fusion Research (PMIF-2019), La Jolla,
                       California (USA), 22 Oct 2019 - 25 Oct
                       2019},
      cin          = {IEK-4 / IEK-1},
      cid          = {I:(DE-Juel1)IEK-4-20101013 / I:(DE-Juel1)IEK-1-20101013},
      pnm          = {174 - Plasma-Wall-Interaction (POF3-174)},
      pid          = {G:(DE-HGF)POF3-174},
      typ          = {PUB:(DE-HGF)1},
      url          = {https://juser.fz-juelich.de/record/874453},
}