Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

T. Happel, A. Bañón Navarro, G. D. Conway, C. Angioni, M. Bernert, M. Dunne, E. Fable, B. Geiger, T. Görler, F. Jenko, R. M. McDermott, F. Ryter, U. Stroth

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Abstract

Additional electron cyclotron resonance heating (ECRH) is used in an ion-temperature-gradient instability dominated regime to increase R / L T e in order to approach the trapped-electron-mode instability regime. The radial ECRH deposition location determines to a large degree the effect on R / L T e. Accompanying scale-selective turbulence measurements at perpendicular wavenumbers between k = 4-18 cm-1 (kρs = 0.7-4.2) show a pronounced increase of large-scale density fluctuations close to the ECRH radial deposition location at mid-radius, along with a reduction in phase velocity of large-scale density fluctuations. Measurements are compared with results from linear and non-linear flux-matched gyrokinetic (GK) simulations with the gyrokinetic code GENE. Linear GK simulations show a reduction of phase velocity, indicating a pronounced change in the character of the dominant instability. Comparing measurement and non-linear GK simulation, as a central result, agreement is obtained in the shape of radial turbulence level profiles. However, the turbulence intensity is increasing with additional heating in the experiment, while gyrokinetic simulations show a decrease.

Original languageEnglish
Article number032503
JournalPhysics of Plasmas
Volume22
Issue number3
DOIs
StatePublished - 1 Mar 2015
Externally publishedYes

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