%0 Journal Article
%A Oelmann, Jannis
%A Wüst, Erik
%A Brezinsek, Sebastijan
%A Li, Cong
%A Zhao, Dongye
%A Rasinski, Marcin
%A Dhard, Chandra Prakash
%A Mayer, Matej
%A Naujoks, Dirk
%A Gao, Yu
%T Hydrogen content in divertor baffle tiles in Wendelstein 7-X
%J Nuclear materials and energy
%V 26
%@ 2352-1791
%C Amsterdam [u.a.]
%I Elsevier
%M FZJ-2021-01057
%P 100943 -
%D 2021
%X Plasma–wall interactions play a crucial role for the performance of fusion devices and the lifetime of plasma-facing components. In this work the results of some plasma–wall interaction processes, namely the erosion/deposition pattern and the fuel content of divertor baffle tiles exposed in Wendelstein 7-X in the initial phase of island divertor, are presented. Net-deposition of carbon with co-deposited oxygen and hydrogen is determined on the graphite tiles after about 1 hour of plasma operation in hydrogen and helium in operation phase OP 1.2a. C is predominately a result of net-erosion of the graphite target plates and oxygen is the strongest intrinsic impurity in Wendelstein 7-X in OP 1.2a. The hydrogen content distribution on a set of tiles exposed in equivalent positions in three of the five modules of the stellarator was quantified for the first time. Ex-situ performed laser-induced breakdown spectroscopy measurements show the depth-resolved fuel content in deposited layers as well as implantation and diffusion in the base material. Complementary, gas analysis after laser-induced ablation offers quantitative hydrogen content determination in the deposited layers up to 1018 hydrogen atoms/cm that is non-uniformly distributed over the 95 mm   125 mm sized tiles. The results show a toroidal asymmetry with 60% more hydrogen in the stellarator module 2 with respect to module 1 as well as a slight top-down asymmetry for the baffle tiles in upper and lower half modules. A clear dependence of the hydrogen content on the surface temperature during plasma exposition in stellarator discharges in standard magnetic divertor configuration with edge transformation 5/5 was not observed.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000628782500060
%R 10.1016/j.nme.2021.100943
%U https://juser.fz-juelich.de/record/890591