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@ARTICLE{Hakola:835981,
      author       = {Hakola, A. and Brezinsek, S. and Douai, D. and Balden, M.
                      and Bobkov, V. and Carralero, D. and Greuner, H. and Elgeti,
                      S. and Kallenbach, A. and Krieger, K. and Meisl, G. and
                      Oberkofler, M. and Rohde, V. and Schneider, P. and
                      Schwarz-Selinger, T. and Lahtinen, A. and De Temmerman, G.
                      and Caniello, R. and Ghezzi, F. and Garcia-Carrasco, A. and
                      Petersson, P. and Bogdanovic Radovic, I. and Siketic, Z. and
                      Wauters, T.},
      title        = {{P}lasma-wall interaction studies in the full-{W} {ASDEX}
                      upgrade during helium plasma discharges},
      journal      = {Nuclear fusion},
      volume       = {57},
      number       = {6},
      issn         = {1741-4326},
      address      = {Vienna},
      publisher    = {IAEA},
      reportid     = {FZJ-2017-05106},
      pages        = {066015},
      year         = {2017},
      abstract     = {Plasma-wall interactions have been studied in the full-W
                      ASDEX Upgrade during its dedicated helium campaign.
                      Relatively clean plasmas with a He content $of  >80\%$
                      could be obtained by applying ion cyclotron wall
                      conditioning (ICWC) discharges upon changeover from D to He.
                      However, co-deposited layers with significant amounts of He
                      and D were measured on W samples exposed to ICWC plasmas at
                      the low-field side (outer) midplane. This is a sign of local
                      migration and accumulation of materials and residual fuel in
                      regions shadowed from direct plasma exposure albeit globally
                      D was removed from the vessel. When exposing W samples to
                      ELMy H-mode helium plasmas in the outer strike-point region,
                      no net erosion was observed but the surfaces had been
                      covered with co-deposited layers mainly consisting of W, B,
                      C, and D and being the thickest on rough and modified
                      surfaces. This is different from the typical
                      erosion-deposition patterns in D plasmas, where usually
                      sharp net-erosion peaks surrounded by prominent
                      net-deposition maxima for W are observed close to the strike
                      point. Moreover, no clear signs of W nanostructure growth or
                      destruction could be seen. The growth of deposited layers
                      may impact the operation of future fusion reactors and is
                      attributed to strong sources in the main chamber that under
                      suitable conditions may switch the balance from net erosion
                      into net deposition, even close to the strike points. In
                      addition, the absence of noticeable chemical erosion in
                      helium plasmas may have affected the thickness of the
                      deposited layers. Retention of He, for its part, remained
                      small and uniform throughout the strike-point region
                      although our results indicate that samples with smooth
                      surfaces can contain an order of magnitude less He than
                      their rough counterparts.},
      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:000399878400002},
      doi          = {10.1088/1741-4326/aa69c4},
      url          = {https://juser.fz-juelich.de/record/835981},
}