[Back]

M. Oberkofler, D. Alegre, F. Aumayr, S. Brezinsek, T. Dittmar, K. Dobes, D. Douai, A. Drenik, M. Köppen, U. Kruezi, C. Linsmeier, C. Lungu, G. Meisl, M. Mozetic, C. Porosnicu, V. Rohde, S. Romanelli, . ASDEX Upgrade Team, JET EFDA Contributors (2014):
"Plasma-wall interactions with nitrogen seeding in all-metal fusion devices: Formation of nitrides and ammonia";
Fusion Engineering and Design, 98-99 (2015), 1371 - 1374.

Nitrogen is routinely used to control the power load to the divertor targets of tokamak fusion reactors.However, its chemical reactivity can have implications on design and operation of a fusion device. Inthis contribution experimental results from recent years on three topics are briefly presented. These arethe formation of nitrides, the sputtering of beryllium in the presence of nitrogen and the production ofammonia. Laboratory experiments have shown that surface nitrides are formed both on beryllium andtungsten upon exposure to energetic nitrogen ions. Erosion rates of Be by energetic N ions are in goodquantitative agreement with modeling. Erosion upon exposure of Be to a mixed N/D plasma is reducedwith respect to a pure D plasma. Finally, the appearance of ammonia has been observed in mixed N/Dplasmas as well as in the exhaust gas of AUG and JET. The production rate in AUG reached 5% of theinjected N atoms in a series of three subsequent N2-seeded discharges

Plasma-wall interactionNitrogen seedingErosionNitrideAmmoniaGas balancea