Speaker
Laura Laguardia
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1026.pdf
45 EPS Conference on Plasma Physics 13326
Impact of He admixture on the ammonia formation in N2 seeded D2
plasmas in the GyM facility
L. Laguardia1, A. Cremona1, G. Gatto1, G. Gervasini1, F. Ghezzi1, G. Granucci1, V. Mellera1,
D. Minelli1, R. Negrotti2, M. Pedroni1, M. Realini2, D. Ricci1, N. Rispoli1, A. Uccello1,
E.Vassallo 1
1
Istituto di Fisica del Plasma - CNR, Via R. Cozzi 53, 20125 Milan, Italy
2
Istituto per la Conservazione e la Valorizzazione dei Beni Culturali - CNR, Via R. Cozzi 53,
20125 Milan, Italy
Impurity seeding with nitrogen is routinely used to reduce the power load to divertor target
plates by radiation in front of the target plates as demonstrate in JET-ILW and AUG [1]. As a
side product of the use of nitrogen as metallic plasma-facing surface, ammonia in significant
amounts can develop. The ammonia formation is a critical issue because, being ammonia
hazardous, could have a significant implication on the operation of the ITER tritium plant
which is prepared to process titrated ammonia in small amounts. In this context, it is
important to try and identify means to reduce/prevent ammonia formation during experiments
with nitrogen seeding in present day devices. In N2 seeded D2 plasmas, ammonia formation
proceeds on the surface of the wall by adsorption of the ND radicals produced by ion-
molecules reactions in low temperature plasmas [2]. Taking into account the mechanism
before mentioned, helium has been identified as the species that could reduce the ammonia
formation because it can potential occupy surface trapping sites in the metallic surface at
which surface reactions leading to ammonia formation take place. The effects on the ammonia
formation of the helium admixture to N2 seeded D2 plasmas were evaluated in GyM linear
device [3]. ND3 produced during the experiments was monitored by optical emission
spectroscopy, through observation of the ND emission band. Ammonia quantification was
obtained by operations involving the collection of the exhaust in LN2 trap and liquid ion
chromatography (LIC) analysis [5]. Results by LIC reveal a decrease in ND3 formation
proportional to the increase of the He ion flux.
[1] M. Oberkofler et al., Journal of Nuclear Materials 438 (2013) S258–S261
[2] L. Laguardia et al., Nuclear materials and Energy 12 (2017) 261-266
[3] G. Granucci, et al., Proceedings of the 36th EPS Conference on Plasma Physics (EPS 2009), 2009, Sofia,
Bulgaria, 2009 ECA 33E, P- 4.148.
[5] L. Laguardia et al., Journal of Nuclear Materials 463 (2015) 680–683
