Increased electron temperature turbulence during suppression of edge localized mode by resonant magnetic perturbations in the DIII-D tokamak

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The first observation of increased electron temperature turbulence during edge localized mode ( ELM) suppression by resonant magnetic perturbations (RMPs) is presented. These are long wavelength fluctuations (k(theta)rho(s) <= 0.2, where k(theta) = poloidal wavenumber and rho(s) = ion sound gyroradius) observed during H-mode plasmas on the DIII-D. This increase occurs only after ELMs are suppressed and are not observed during the initial RMP application. The (T) over tilde (e)/T-e increases (>60%) are coincident with changes in normalized density and electron temperature gradients in the region from the top of the pedestal outward to the upper portion of the steep edge gradient. Density turbulence (k(theta)rho(s) <= 0.4) in this location was also observed to increase only after ELM suppression. These results are significant since they indicate that increased gradient-driven turbulent transport is one possible mechanism to regulate and maintain ELM-free H-mode operation. Investigation of linear stability of drift wave instabilities using the CGYRO code [ Candy et al., J. Comput. Phys. 324, 73 (2016)] shows that the dominant mode moves closer to the electron mode branch from the ion mode branch only after ELMs are suppressed, correlated with the increased turbulence. The increased turbulence during ELM suppression, rather than with the initial RMP application, indicates that the often observed RMP induced "density pump-out" cannot be attributed to long wavelength edge turbulence level changes. Published by AIP Publishing.
Publisher
AMER INST PHYSICS
Issue Date
2017-11
Language
English
Article Type
Article
Citation

PHYSICS OF PLASMAS, v.24, no.11, pp.112305

ISSN
1070-664X
DOI
10.1063/1.4999785
URI
http://hdl.handle.net/10203/272784
Appears in Collection
NE-Journal Papers(저널논문)
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