TY  - JOUR
AU  - Zhao, Dongye
AU  - Yi, R.
AU  - Oelmann, J.
AU  - Brezinsek, S.
AU  - Rasinski, M.
AU  - Gao, Y.
AU  - Mayer, M.
AU  - Dhard, C. P.
AU  - Krause, M.
TI  - Ex situ analysis of W7-X divertor plasma-facing components by picosecond laser diagnostics
JO  - Physica scripta
VL  - T171
SN  - 1402-4896
CY  - Stockholm
PB  - The Royal Swedish Academy of Sciences
M1  - FZJ-2020-03051
SP  - 014018 -
PY  - 2020
AB  - A key question of long-pulse operation in the stellarator Wendelstein 7-X (W7-X) is the net erosion of plasma-facing components (PFCs), which determines W7-X PFC lifetimes as well as the impact on the impurity influx to the plasma. In order to judge the erosion and deposition balance at the passively cooled graphite divertor, a set of exchangeable graphite tiles with marker layer stripes consisting of 5–10 μm C deposited on a 200 nm thick Mo interlayer were installed as an integral part of the divertor surface and removed at the end of the first operational phase for post-operational analysis. Laser-induced breakdown spectroscopy (LIBS) combined with laser-induced ablation-quadrupole mass spectrometry (LIA-QMS) were used for further analysis. The LIBS results show that the erosion-dominated regions are close to the location of the strike lines in standard magnetic configuration of W7-X optimised for the island divertor concept. Almost the complete C/Mo marker layer is eroded in these regions, providing an average erosion rate of 4.3 nm s−1 in the 2481 s plasma seconds of the campaign. In parallel, only a little deposition at the edge of the divertor tiles, where Mo is observed on the bulk graphite material was found. Furthermore, LIA-QMS showed a high hydrogen content on uncoated bulk graphite areas, while a lower hydrogen concentration was detected in the erosion-dominated zone, caused by the high surface temperature at the strike line during plasma operation.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000520000600018
DO  - DOI:10.1088/1402-4896/ab3ee1
UR  - https://juser.fz-juelich.de/record/878798
ER  -