Gyrokinetic study of turbulence suppression in a JET-ILW power scan. (15th September 2016)

• Record Type: Journal Article
• Authors: Doerk, H; Challis, C; Citrin, J; Garcia, J; Görler, T; Jenko, F
• Other Names: collab.
• Is Part Of: Plasma physics and controlled fusion. Volume 58:Number 11(2016:Nov.)
• Publication Date: 2016-09-15
• Subjects: tokamak -- gyrokinetic simulation -- thermal transport -- electromagnetic turbulence; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/0741-3335/58/11/115005
• Languages: English
• ISSNs: 0741-3335

Abstract

Abstract: For exploring tokamak operation regimes that deliver both high β and good energy confinement, power scans at JET with ITER-like wall have been performed. Relatively weak degradation of the confinement time coincides with increased core temperature of the ions at high power. The changes in core turbulence characteristics during a power scan with an optimized (broad) q profile are analyzed by means of nonlinear gyrokinetic simulations. The increase in β is crucial for stabilizing ion temperature gradient driven turbulence, accompanied by increased ion to electron temperature ratio, the presence of a dynamic fast ion species, as well as the geometric stabilization by increased thermal and suprathermal pressure. A sensitivity study with respect to the q profile reveals that electromagnetic effects are more pronounced at larger values of q . Further, it is confirmed that turbulence suppression due to rotation becomes less effective in such strongly electromagnetic systems. Electrostatic simplified models may thus perform well in present-day devices, in which high β is often correlated with high rotation, but provide poor extrapolation towards low rotation devices. Implications for ITER and reactor plasmas are discussed.