Influence of He and Ar injection on ammonia production in N2/D2 plasma in the medium flux GyM device

Mass-spectrometry results showed that ND3 is formed only during the plasma phase of the experiment while LIC showed that ammonia production increases with Te and with the total neutral pressure. Optical Emission Spectroscopy confirms the presence of ND species in all the cases studied. The addition of He and Ar in the N2/D2 plasma, not modifing Te and ne, causes a reduction of ammonia formation, that is negligible in the case of Ar addition, while in the case of He reaches 80%. This suggests that He modifies the physical chemical process occurring at the wall, where the adsorbed He inhibits the reactions leading to ammonia formation at the metallic surface of the vessel. These results confirm the active role of a metallic surface in ammonia production and indicate He injection as a promising solution to limit the formation of the tritiated ammonia in the N seeded plasma of ITER.