TY - JOUR
T1 - Theoretical aspects and practical implications of the heuristic drift SOL model
AU - Goldston, R. J.
N1 - Funding Information:
The author thanks Richard Pitts for his leadership in the effort to uncover the physics of the near SOL in limiter plasmas. He also thanks A. Chankin for helpful discussions. For early access to data, the author thanks Jan Horaçek, Renaud Dejarnac and the COMPASS team, Peter Stangeby and the DIII-D team, Brian LaBombard and the C-MOD team, Fedorici Nespoli and the TCV team, and Gilles Arnoux and the JET team. This work supported by DOE Contract No. DE-AC02-09CH11466 .
Publisher Copyright:
© 2015 Published by Elsevier B.V.
PY - 2015/7/22
Y1 - 2015/7/22
N2 - Abstract The heuristic drift (HD) model for the tokamak power scrape-off layer width provides remarkable agreement in both absolute magnitude and scalings with the measured width of the exponential component of the heat flux at divertors targets, in low gas-puff H-Mode tokamaks. This motivates further exploration of its theoretical aspects and practical implications. The HD model requires a small non-ambipolar electron particle diffusivity ∼10-2 m2/s. It also implies large parallel heat flux in ITER and suggests that more radical approaches will be needed to handle the ∼20 GW/m2 parallel heat flux expected in Demo. Remarkably, the HD model is also in good agreement with recent near-SOL heat flux profiles measured in a number of limiter L-Mode experiments, implying ubiquity of the underlying mechanism. Finally, the HD model suggests that the H-Mode and more generally Greenwald density limit may be caused by MHD instability in the SOL, rather than originating in the core plasma or pedestal. If the SOL width in stellarators is set by magnetic topology rather than by drifts, this would be consistent with the absence of the Greenwald density limit in stellarators.
AB - Abstract The heuristic drift (HD) model for the tokamak power scrape-off layer width provides remarkable agreement in both absolute magnitude and scalings with the measured width of the exponential component of the heat flux at divertors targets, in low gas-puff H-Mode tokamaks. This motivates further exploration of its theoretical aspects and practical implications. The HD model requires a small non-ambipolar electron particle diffusivity ∼10-2 m2/s. It also implies large parallel heat flux in ITER and suggests that more radical approaches will be needed to handle the ∼20 GW/m2 parallel heat flux expected in Demo. Remarkably, the HD model is also in good agreement with recent near-SOL heat flux profiles measured in a number of limiter L-Mode experiments, implying ubiquity of the underlying mechanism. Finally, the HD model suggests that the H-Mode and more generally Greenwald density limit may be caused by MHD instability in the SOL, rather than originating in the core plasma or pedestal. If the SOL width in stellarators is set by magnetic topology rather than by drifts, this would be consistent with the absence of the Greenwald density limit in stellarators.
UR - http://www.scopus.com/inward/record.url?scp=84937739507&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84937739507&partnerID=8YFLogxK
U2 - 10.1016/j.jnucmat.2014.10.080
DO - 10.1016/j.jnucmat.2014.10.080
M3 - Article
AN - SCOPUS:84937739507
SN - 0022-3115
VL - 463
SP - 397
EP - 400
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
M1 - 48577
ER -