Experiments and gyrokinetic simulations of TCV plasmas with negative triangularity in view of DTT operations

Abstract

Abstract Negative Triangularity (NT) scenarios in TCV have been compared to Positive Triangularity (PT) scenarios using the same plasma shapes foreseen for DTT tokamak operations. The experiments provided a NT/PT L-mode pair and a PT H-mode with different heating mixes. Regardless of the heating mix, NT L-modes always reached higher values of plasma pressure with respect to PT L-modes with the same power and recovered the central pressure of PT H-mode scenarios heated with up to twice the injected power. The experimental analysis shows that this enhanced performance in NT is due to larger temperature and density gradients close to the edge (ρtor = [0.8 − 1.0]) and higher values of pressure at the separatrix. Local gyrokinetic simulations agree with the experimental results and are able to catch the effect of shaping alone. Integrated modeling performed with ASTRA-TGLF reproduces reasonably well the PT shot but is not able to fully capture the improvements in the NT shot.