Simulation study of the influence of the cross-field anomalous diffusion on the tungsten impurity transport in the scrape-off layer with activated drifts

Abstract

Tungsten (W) impurity eroded from the divertor target can degrade the confinement performance of future fusion reactors. The mechanism of the effect of E × B drift on the W transport in the scrape-off layer (SOL) was investigated with a fixed cross-field anomalous particle diffusion coefficient for W ions (D_⊥,W) of 1 m²s⁻¹ in our previous simulation work, which indicates that the W flux entering the confined region (Γ_enter) and mean W concentration in the confined region ($C_W^{\mathrm{avg}}$) can be increased by more than one order of magnitude by drifts. In this work, the influence of the cross-field anomalous diffusion on the W transport in the SOL is further investigated. The basic flow pattern of the W ion flux (Γ_W) keeps when D_⊥,W varying from 0.5 to 3 m²s⁻¹, and Γ_enter mainly comes from the hotter divertor region. Results show that D_⊥,W value affects the W leakage from divertor region and entry into confined region. Therefore, Γ_enter and $C_W^{\mathrm{avg}}$ both decrease with increasing D_⊥,W. Mechanisms for cases w/wo drifts are compared.