Simulation on the transition of electrostatic instabilities in EAST steady-state scenario

Abstract

The parameter dependence of transition between electrostatic instabilities is studied using gyrokinetic simulation based on a real discharge of steady-state scenario in the Experimental Advanced Superconducting Tokamak. The scan of radial locations shows that trapped electron mode (TEM) dominates around the core while the ion temperature gradient mode (ITG) simultaneously dominates outside. The maximum growth rate of TEM appears around ρ = 0.24, where the maximum electron temperature gradient R/L Te locates, ρ is the normalized poloidal flux. Effects of the parameters on the transition between TEM and ITG instability are studied at ρ = 0.24. It is found that TEM dominates in the scanning with individually changing R/L Te from 2.50 to 25.02 or the density gradient R/L n from 1.38 to 13.76. Meanwhile, the electron-ion temperature ratio T e/T i is found to destabilize TEM, the effect of T e is more sensitive than that of T i. The dominant instability diagrams in the (R/L Te, R/L Ti) plane at different T e/T i and R/L n are numerically obtained, which clearly show the parameter range of the dominant TEM or dominant ITG instability region. It is found that the dominant TEM region becomes narrower in the plane by decreasing R/L n when T e/T i > 0.5.