ENN is dedicated to exploring the commercialization of fusion energy by utilizing the EHL-2 spherical device as a next-generation platform. This research focuses on evaluating turbulent transport in the core ion transport barrier region of EHL-2, specifically investigating the effects of plasma β on transport features. Gyrokinetic simulation results indicate that under the typical operation scenario, transport is predominantly driven by electrostatic ion temperature gradient modes and trapped electron modes. Nevertheless, as the total β approaches 20%, nonlinear excitation of the electromagnetic mode is discovered, leading to an explosive increase in transport as well as zonal flow erosion due to enhanced magnetic fluctuations. It is also found that the external E × B rotational shear is only effective in suppressing the turbulence when the electromagnetic modes are linearly stable or nonlinearly unstable.
This paper investigates the effects of high plasma beta (β) on turbulent transport in the core ion transport barrier region of the EHL-2 spherical torus device. Gyrokinetic simulations show that as β approaches 20%, electromagnetic modes become excited, leading to increased transport and erosion of zonal flows.