This title appears in the Scientific Report :
2021
Please use the identifier:
http://hdl.handle.net/2128/29933 in citations.
Please use the identifier: http://dx.doi.org/10.1088/1741-4326/abf056 in citations.
The role of edge plasma parameters in H-mode density limit on the JET-ILW
The role of edge plasma parameters in H-mode density limit on the JET-ILW
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 pe...
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Personal Name(s): | Sun, H. J. |
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Goldston, R. J. / Huber, A. (Corresponding author) / Xu, X. Q. / Flanagan, J. / McDonald, D. C. / de la Luna, E. / Maslov, M. / Harrison, J. R. / Militello, F. / Fessey, J. / Cramp, S. | |
Contributing Institute: |
Plasmaphysik; IEK-4 Modellierung von Energiesystemen; IEK-10 |
Published in: | Nuclear fusion, 61 (2021) 6, S. 066009 - |
Imprint: |
Vienna
IAEA
2021
|
DOI: |
10.1088/1741-4326/abf056 |
Document Type: |
Journal Article |
Research Program: |
Plasma-Wand-Wechselwirkung |
Link: |
Published on 2021-04-28. Available in OpenAccess from 2022-04-28. Restricted |
Publikationsportal JuSER |
Please use the identifier: http://dx.doi.org/10.1088/1741-4326/abf056 in citations.
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. |