Jena 2013 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 21: Plasma- Wand- Wechselwirkung

P 21.7: Vortrag

Donnerstag, 28. Februar 2013, 18:15–18:30, HS 3

Nitrogen-Deuterium Bombardment of Tungsten and Analysis with XPS — •Gerd Meisl, Klaus Schmid, and Christian Linsmeier — Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Boltzmannstr. 2, 85748 Garching, Deutschland

One of the critical problems in fusion experiments is the power load on the divertor. To limit this load it is desirable to increase the radiated power by puffing impurities into the plasma. Nitrogen has been established as standard gas to control the divertor heat load at ASDEX Upgrade. However, formation, stability, and erosion of tungsten nitride layers formed by the implantation of nitrogen from the plasma into the tungsten walls are still poorly understood. An improved understanding of these processes is required to predict the migration of nitrogen in a fusion device. We therefore started comprehensive studies, including small laboratory experiments, tokamaks and computer simulations to gather and combine additional information. To measure the N accumulation and re-erosion experiments in a XPS system were performed, allowing to follow the surface composition evolution while bombarding the W surface with N or D from ion guns. A comparison with Tridyn simulations of nitrogen implantation at low temperatures showed reasonable agreement. Erosion of tungsten nitride with deuterium ions matches Tridyn simulations if the surface binding energy of nitrogen is set to zero. Furthermore it was found that the nitrogen content is more sensitive to the temperature during implantation than during consecutive heating.