Recent Progress in the Understanding of H Transport and Trapping in W

Wall Forum

  • Datum: 03.05.2017
  • Uhrzeit: 15:30 - 16:30
  • Vortragende(r): Klaus Schmid
  • E2M
  • Ort: Garching
  • Raum: Seminarraum D3
  • Gastgeber: IPP
The retention of hydrogen isotopes (H, D and T) in the first, plasma exposed wall isone of the key concerns for the operation of future long pulse fusion devices. It affects theparticle-, momentum and energy balance in the scrape-off layer as well as the retention ofhydrogen isotopes (HIs) and their permeation into the coolant. The currently acceptedpicture that is used for interpreting current laboratory and tokamak experiments is thatof diffusion hindered by trapping at lattice sites. This paper summarises recent resultsthat show that this current picture of how HIs are transported and retained in W needsto be extended: The modification of the surface (e.g. blistering) can lead to the formationof fast loss channels for near surface H. Trapping at single occupancy traps with fixed de-trapping energy fails to explain isotope exchange experiments, instead a trapping modelwith multi occupancy traps and fill level dependent de-trapping energies is required. Thepresence of interstitial impurities like N or C affects the solute HI diffusion coefficient. Thepresence of HIs during damage creation by e.g. neutrons stabilises defects and reducesdefect annealing at elevated temperatures.
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