Influence of the tungsten surface chemical state on the ammonia formation using low-pressure N2-H2 plasmas

The fusion reactor ITER will use nitrogen gas to spread the power loads on the tungsten (W) divertor, which extracts heat and ash produced by the fusion reaction. However, once ionised in the fusion plasma, the nitrogen ions and radicals will form stable compounds with the fusion fuel i.e. hydrogen isotopes deuterium (D) and tritium (T). As a result, ammonia isotopologues (e.g., ND 2 T) will be formed. As a polar molecule, ammonia will stick on the reactor walls, imposing concerns on the tritium safety limit for ITER 1 . Hence, it is crucial to investigate the conditions at which ammonia is produced and identify strategies to destroy/process it.