Berlin 2014 – scientific programme
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P: Fachverband Plasmaphysik
P 16: Helmholtz Graduate School for Plasma Physics I
P 16.2: Topical Talk
Wednesday, March 19, 2014, 14:25–14:50, SPA HS202
Nitrogen migration and retention in ASDEX Upgrade — •G. Meisl1, K. Schmid1, M. Oberkofler1, K. Krieger1, S.W. Lisgo2, L. Aho-Mantila3, F. Reimold1, V. Rohde1, and ASDEX Upgrade Team1 — 1Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Boltzmannstraße 2, 85748 Garching, Germany — 2ITER Organization, FST, Route de Vinon, CS 90 046, 13067 Saint Paul Lez Durance Cedex, France — 3VTT, FI-02044 VTT
To limit the power load in high-power plasma operation, impurity seeding is mandatory. Nitrogen has been established as optimal choice in ASDEX Upgrade. However, as N is subject to wall pumping, a self-consistent model of the N source flux distribution is required.
N retention in tungsten was studied in laboratory experiments under well-defined exposure conditions. The applicability of the so established model of W-N interaction was tested by experiments in ASDEX Upgrade. W samples were exposed to plasmas with and without N seeding and analyzed by ion beam analysis. Using these data as boundary condition, N transport and re-distribution in the plasma were studied by self-consistent WallDYN-DIVIMP modelling. The dynamic change of the N erosion source at plasma exposed W surfaces was then computed by WallDYN using an improved W-N surface model. First simulations show, in agreement with the experiment, a strong rise of the N re-erosion flux within the first second. By this approach the experimental results from sample analysis, spectroscopy and N pumped by the vacuum system can be interpreted for the first time within a unified self-consistent model.