Erlangen 2018 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 20: Plasma Wall Interaction II - Poster
P 20.5: Poster
Mittwoch, 7. März 2018, 16:15–18:15, Zelt West
Assessment of nitrogen enrichment in plasma discharges cooled by nitrogen gas puffing in ASDEX Upgrade — •Thomas Reichbauer1,2, Volker Rohde1, Aleksander Drenik1, and the ASDEX Upgrade Team1 — 1Max Planck Institute for Plasma Physics, Garching, Germany — 2Physics Department E28, TUM, Garching, Germany
To avoid divertor damage by overheating, intrinsic divertor radiation which dissipates power is too low. In ASDEX Upgrade (AUG) nitrogen is seeded into the divertor to reduce its power load. But nitrogen seeding leads to ammonia formation which could become an issue for gas handling plants and cryo pumps of future fusion devices. A direct measurement of the interacting nitrogen with D on the surface is not possible. The produced ammonia is measured with residual gas analyzers. The detection of ammonia is still not a straight forward procedure because all molecules are created in a mixed D/H environment with unknown ratio. Therefore the ratios of H2O, CH4 and NH3 overlap. A fit routine was constructed to gain partial pressures of the different gases. For working reliably, the calibration is a key aspect. After N2 seeded discharges nitrogen is implemented in walls and stays in AUG for the following ones. The connection of nitrogen and ammonia is established in the following discharges. This could give a better insight of the amount of interacting nitrogen during N2 puffing. First results on the NH3/N2 ratios during legacy discharges are presented and how they could be used to gain information about the formation mechanism of ammonia during N2 seeded discharges.