Analysis of edge stability for models of heat flux width. (August 2017)

• Record Type: Journal Article
• Authors: Makowski, M.A.; Lasnier, C.J.; Leonard, A.W.; Osborne, T.H.
• Is Part Of: Nuclear materials and energy. Volume 12(2017)
• Page Start: 1010
• Page End: 1014
• Publication Date: 2017-08
• Subjects: Nuclear energy -- Periodicals; Nuclear fuels -- Periodicals; Nuclear reactors -- Materials -- Periodicals; Radioactive substances -- Periodicals; 621.4833
• DOI: 10.1016/j.nme.2017.04.008
• Languages: English
• ISSNs: 2352-1791

Abstract

Highlights: This paper provides experimental results and theoretical analysis pertinent to the critical gradient model for the heat flux width. ․ The data is found not to support this theory as the measured pressure gradient lies well below the theoretical ideal infinite-n critical pressure gradient as calculated from the BALOO code. ‥ The experimental results are in very good agreement with heuristic drift model in that the predicted normalized pressure gradient scales in accordance with that obtained from equlibrium reconstructions. Abstract: Detailed measurements of the ne, Te, and Ti profiles in the vicinity of the separatrix of ELMing H-mode discharges have been used to examine plasma stability at the extreme edge of the plasma and assess stability dependent models of the heat flux width. The results are strongly contrary to the critical gradient model, which posits that a ballooning instability determines a gradient scale length related to the heat flux width. The results of this analysis are not sensitive to the choice of location to evaluate stability. Significantly, it is also found that the results are completely consistent with the heuristic drift model for the heat flux width. Here the edge pressure gradient scales with plasma density and is proportional to the pressure gradient inferred from the equilibrium in accordance with the predictions of that theory.