Observation of a Critical Gradient Threshold for Electron Temperature Fluctuations in the DIII-D Tokamak
- White, Anne E.
- Hillesheim, J. C.
- DeBoo, J. C.
- Peebles, W. A.
- Carter, T. A.
- Wang, G.
- Rhodes, T. L.
- Schmitz, L.
- McKee, G. R.
- Yan, Z.
- Staebler, G. M.
- Burrell, K. H.
- Doyle, E. J.
- Holland, C.
- Petty, C. C.
- Smith, S. P.
- White, A. E.
- Zeng, L.
DOIAbstract
A critical gradient threshold has been observed for the first time in a systematic, controlled experiment for a locally measured turbulent quantity in the core of a confined high-temperature plasma. In an experiment in the DIII-D tokamak where L[subscript T[subscript e]][superscript -1]=|∇T[subscript e]|/T[subscript e] and toroidal rotation were varied, long wavelength (k[subscript θρs]≲0.4) electron temperature fluctuations exhibit a threshold in L[subscript T[subscript e]][superscript -1]: below, they change little; above, they steadily increase. The increase in δT[subscript e]/T[subscript e] is concurrent with increased electron heat flux and transport stiffness. Observations were insensitive to rotation. Accumulated evidence strongly en...
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