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@ARTICLE{Sun:904076,
author = {Sun, H. J. and Goldston, R. J. and Huber, A. and Xu, X. Q.
and Flanagan, J. and McDonald, D. C. and de la Luna, E. and
Maslov, M. and Harrison, J. R. and Militello, F. and Fessey,
J. and Cramp, S.},
title = {{T}he role of edge plasma parameters in {H}-mode density
limit on the {JET}-{ILW}},
journal = {Nuclear fusion},
volume = {61},
number = {6},
issn = {0029-5515},
address = {Vienna},
publisher = {IAEA},
reportid = {FZJ-2021-05646},
pages = {066009 -},
year = {2021},
abstract = {A study of a dataset of JET H-mode plasma with the Be/W
ITER-like wall (JET-ILW) shows that reaching the edge MHD
ballooning limit leads to confinement degradation. However,
unlike JET plasmas with a carbon wall (JET-C), the JET-ILW
plasmas stay in a marginal dithering phase for a relatively
long period, associated with a higher $(≈20\%)$ H-mode
density limit (HDL) than JET-C equivalents. This suggests
that ITER could be operated in H-mode with higher density
than the scaling based on carbon wall devices, but likely
with a dithering phase plasma with lower confinement. A new,
reliable estimator for JET Er, min has been derived by
combining HRTS measurements of pedestal gradient and
edge-SOL decay lengths. JET radial Er ETB wells are observed
in the range of −15 to −60 kV m−1 in high performance
H-modes, consistent with previous CXRS results in ASDEX
Upgrade. The results imply that a higher positive E × B
shear in the near SOL plays a role in sustaining a marginal
phase in JET-ILW which leads to a higher HDL than that in
JET-C. The results of the JET-ILW dataset show agreement
with the Goldston finite collisionality HD model for SOL
broadening at high collisionality. A hypothesis for the
dithering H-mode phase is proposed: as ne,SOL increases,
ν∗,SOL increases, SOL broadens, Er shear decreases,
triggers L-mode; ne drops, ν∗,SOL decreases, SOL becomes
narrower, and Er shear increases, triggering H-mode,
resulting in a cycle of H–L–H- oscillations. For burning
plasma devices, such as ITER, operating just below the MHD
limit for the dithering phase could be a promising regime
for maximising core density, and fusion performance while
minimising plasma-material interaction. The oscillatory
signal during the dithering phase could be used as a
precursor of undesirable plasma performance for control
purposes.},
cin = {IEK-4 / IEK-10},
ddc = {620},
cid = {I:(DE-Juel1)IEK-4-20101013 / I:(DE-Juel1)IEK-10-20170217},
pnm = {134 - Plasma-Wand-Wechselwirkung (POF4-134)},
pid = {G:(DE-HGF)POF4-134},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000645584300001},
doi = {10.1088/1741-4326/abf056},
url = {https://juser.fz-juelich.de/record/904076},
}