TY  - JOUR
AU  - Wauters, Tom
AU  - Goriaev, Andrei
AU  - Alonso, Arturo
AU  - Baldzuhn, Juergen
AU  - Brakel, Rudolf
AU  - Brezinsek, Sebastijan
AU  - Dinklage, Andreas
AU  - Grote, Heinz
AU  - Fellinger, Joris
AU  - Ford, Oliver P.
AU  - König, Ralf
AU  - Laqua, Heinrich
AU  - Matveev, Dmitry
AU  - Stange, Torsten
AU  - Vanó, Lilla
TI  - Wall conditioning throughout the first carbon divertor campaign on Wendelstein 7-X
JO  - Nuclear materials and energy
VL  - 17
SN  - 2352-1791
CY  - Amsterdam [u.a.]
PB  - Elsevier
M1  - FZJ-2018-07202
SP  - 235 - 241
PY  - 2018
AB  - Controlling the recycling of hydrogen and the release of impurities from the plasma facing components proved to be essential and challenging throughout the first divertor campaign on W7-X. This paper discusses the conditioning requirements throughout the first divertor campaign on Wendelstein 7-X. Baking at 150°C and glow discharge conditioning (GDC) in H2 is performed after the initial pump down of the vacuum vessel. Experimental programs in hydrogen are interlaced with He discharges to desaturate the wall from hydrogen, recover good recycling conditions and hence establish plasma density control. Optimized He ECRH wall conditioning procedures consisted of sequences of short discharges with fixed duty cycle. He-GDC remained however needed before each experimental day to fully offset the hydrogen inventory build-up. A significant increase in the divertor temperature is observed throughout an operational day, enhancing outgassing of CO and H2O. Preliminary recombination-diffusion modelling of hydrogen outgassing suggests enhanced diffusion to deeper surface layers with increasing wall temperature, which results in better wall pumping. This indicates that the experienced plasma performance degradation throughout an operational day results from increased impurity outgassing at higher wall temperature rather than hydrogen saturation of the wall.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000454165000033
DO  - DOI:10.1016/j.nme.2018.11.004
UR  - https://juser.fz-juelich.de/record/858314
ER  -