%0 Journal Article
%A Dittmar, T.
%A Loarer, T.
%A Drenik, A.
%A Bourdelle, C.
%A Brezinsek, S.
%A Desgranges, C.
%A Douai, D.
%A Fedorczak, N.
%A Guirlet, R.
%A Gunn, J.
%A Meyer, O.
%A Laguardia, L.
%A Tsitrone, E.
%T Long pulse D 2 and N 2 seeded discharges on the upper actively cooled tungsten divertor of WEST
%J Physica scripta
%V T171
%@ 1402-4896
%C Stockholm
%I The Royal Swedish Academy of Sciences
%M FZJ-2021-01496
%P 014074 -
%D 2020
%X A series of L-mode discharges in upper single null configuration with more than 30 s duration were performed in the WEST tokamak with the strike line on actively cooled tungsten-coated divertor components. This series of discharges accumulated 20 min of plasma and a strike point fluence of $\approx 2\times {10}^{25}\,{{\rm{m}}}^{-2}$ in two days of operation in attached conditions. The discharges showed good density control, no tungsten accumulation and overall very benign thermal behaviour of the upper divertor. A subset of the discharges were seeded with nitrogen either in the divertor or midplane region to study plasma–wall interaction and associated ammonia formation in this weakly pumped scenario with all-tungsten plasma-facing components. While ammonia signals remained too weak for useful analysis, a strong dependence of nitrogen plasma penetration efficiency and residence time on the injection location was found. This hints towards a currently underestimated plasma-near nitrogen reservoir in these tokamak discharges in divertor configuration.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000546774400001
%R 10.1088/1402-4896/ab753f
%U https://juser.fz-juelich.de/record/891411