The performance of equilibrium radial electric field shear on microturbulence with different magnetic shears in tokamak plasmas

Abstract

Global gyrokinetic particle simulations show that equilibrium radial electric field (Er) shear reduces the linear growth rate, ion heat conductivity, and nonlinear turbulence amplitude for both the ion temperature gradient (ITG) and kinetic ballooning mode (KBM) microturbulence with tilting the poloidal mode structure. Increase in the magnetic shear enhances the stabilizing performance of the Er shear on linear growth rate for ITG case but has no effect on that for KBM case. The radial correlation length of the ITG turbulence is decreased by increasing the magnetic shear in a weak ion diamagnetic flow shear condition with low β, leading to a reduction in effective ExB shearing rate, which weakens the suppression performance of the Er shear on ITG turbulence amplitude. In contrast, under a larger ion diamagnetic flow shear for higher β, increase in magnetic shear strengthens the suppression performance of the Er shear on KBM turbulence amplitude due to increase in the effective shearing rate by increasing the radial correlation length of the turbulence.