The role of kinetic effects on the tungsten impurity transport in the boundary plasma of EAST

A kinetic impurity transport model has been implemented in the Monte-Carlo code DIVIMP to investigate W transport in the boundary plasma of EAST under varied divertor conditions. Background plasmas representing high-recycling and detached divertor conditions with D₂ and Ne injection in low-confinement mode (L-mode) and high-confinement mode (H-mode) plasmas are provided by the SOLPS simulations, and W transport is then simulated with the DIVIMP code. The inclusion of kinetic effects is found to significantly reduce the W thermal force compared to the conventional fluid model, not only in low collisionality (ν* < 20) conditions, but also in low ion temperature (Ti) and high effective charge (Zeff) conditions. As the divertor condition varies from the high-recycling to the detached regime with Ne injection, kinetic effects on divertor W retention are enhanced by the decrease of ion temperature and the increase of effective charge. In high-density H-mode plasmas, the kinetic correction on the W thermal force is weaker than in low-density L-mode plasmas. However, the strong friction force in the high-density H-mode cases makes the influence of kinetic effects on W retention more significant, resulting in a reduction of core W density by more than two orders of magnitude. In addition, comparisons with the original Garching flux-limit correction in DIVIMP show that the flux-limit overestimates W thermal force and core W density, especially under impurity seeding conditions. Therefore, explicit kinetic modeling of the thermal force is required for accurate description of W transport in the boundary plasma of tokamaks.