PPPL-5445
Comparison of heat flux profile evolution during different types
of edge localized modes in the National Spherical Torus Experiment
PPPL Authors: K.F. Gan, R. Maingi, J-W. Ahn, A.G.
McLean, T.K. Gray and B.D. Wirth
Abstract:
TIn this paper, the divertor heat flux profile evolution is compared
during type I, type III, and type V edge localized modes (ELMs) in
the National Spherical Torus Experiment (NSTX). Small type V ELMs
are routinely observed in many discharges, resulting in
less
than or equal to
50% transient increase
in peak heat flux; as compared with true ELM-free phases in
discharges, the integral power decay width(λint) is ~ 300% larger
with Type V ELMs than without. During Type III ELMs, the peak heat
flux can increase by up to 300% relative to the inter-ELM heat flux,
and the heat profile width decreases as compared to the inter-ELM
width, which is dominated by type V ELMs that routinely occur
between the type III ELMs in these discharges. The peak heat flux
can increase by up to 1000% during type I ELMs, with a significant
contraction of the profile width. Finally analysis of the time
evolution of the heat flux profiles shows instances where the peak
heat flux peaks during the ELM decay phase, resulting in a very
narrow profile and high PFC heating.