Gyrokinetic Simulation of Turbulence in the High-β_N Discharge on the Experimental Advanced Superconducting Tokamak

Abstract

Experiments on Experimental Advanced Superconducting Tokamak (EAST) were performed with high normalized beta (${{\beta }_{N}}\sim 1.9$) and favorable energy confinement (${{H}_{{98,y2}}}\sim 1.1$) for the operating space achieved in EAST. Gyrokinetic simulations were carried out for four different ${{\beta }_{N}}$ cases with the experimental plasma parameters and tokamak equilibrium data. It was found that the favorable confinement is effectively maintained when ${{\beta }_{N}}$ increases to 1.9. The radial distribution of potential fluctuation during turbulence saturation phase is consistent with that of thermal transport diffusivity. Turbulence with higher toroidal modes becomes important as ${{\beta }_{N}}$ increases, and zonal flow shearing rate suppresses the turbulence when ${{\beta }_{N}}$ increases to 1.9, which is responsible for the well-maintained confinement.