Publication Date:
2015-03-10
Description:
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 ( k ⊥ ρ s = 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.
Print ISSN:
1070-664X
Electronic ISSN:
1089-7674
Topics:
Physics