This work presents a dedicated study on the improved core energy confinement observed during neon-seeded I-mode detachment experiments on EAST. The experimental results demonstrate that neon seeding facilitates divertor detachment, as evidenced by the rollover in the ion saturation current and the reduction in the target surface temperature, while simultaneously avoiding I–L back-transition. Notably, an increase in the plasma stored energy and the confinement factor is achieved, which is primarily attributed to the elevated core electron and ion temperatures, despite a slight degradation of the pedestal. Higher neon seeding rates are found to promote deeper detachment and greater core confinement improvement with modest neon concentration and radiative loss fraction. Power balance analysis using the ONETWO code reveals a significant reduction in ion and electron thermal diffusivity after neon seeding. The predictions of plasma profiles using the TGYRO code confirm the increment of core temperature. Subsequent quasi-linear gyrokinetic analysis with the trapped gyro-Landau fluid model identifies that core heat transport is predominantly driven by trapped electron modes (TEMs). Our study demonstrates that neon seeding stabilizes TEMs, primarily through enhanced collisionality, with the main ion dilution playing a minor role. This suppression of TEM turbulence leads to a reduction in heat fluxes, which outweighs the radiative cooling effect and thereby improves the core energy confinement. These results demonstrate that neon impurity seeding can enable the simultaneous achievement of divertor detachment and enhanced core confinement in I-mode operation on EAST, offering a valuable reference for solving core–edge integration issues.
The effect of neon seeding on plasma edge transport in EAST