SOLPS-ITER modeling of neon-seeded EAST plasmas under connected double-null configurations and its impact on tungsten impurity behaviors

The SOLPS-ITER edge modeling package was employed to numerically investigate neon (Ne)-seeded EAST plasmas under connected-double-null configurations, focusing on Ne impurity transport and its impacts on tungsten (W) impurity behaviors. Results reveal that E× B drift significantly modifies the target profiles of plasma density (ne) and temperature (Te) by modulating divertor particle transport, thereby strongly influencing W sputtering. Without drifts, radial particle transport into the far divertor SOL is minimal, resulting in low ne and high Te, which in turn leads to significant W sputtering in this region. Drifts shift the peak positions of ne and Te at the target, and generate significant in-out/up-down divertor asymmetries. Notably, in-out divertor asymmetry in Te exhibits a distinct dependence on Ne puffing rate (ΓNe,puff) compared to single-null configurations. W sputtering can be effectively reduced by increasing ΓNe,puff, but only when radial particle transport into the far divertor SOL is significantly enhanced by E× B drift. Under drift-free conditions, low ΓNe,puff leads to stagnation points for the poloidal Ne (W) velocity within divertor regions, causing a significant Ne (W) divertor leakage through the near SOL. This leakage can be alleviated by increasing ΓNe,puff. Conversely, at high ΓNe,puff, influences of Ne on the deuterium ionization source in the divertor regions leads to the redistribution of Ne density from the upper to lower divertor through the main SOL. In full-drift scenarios, the E× B drift dominates the poloidal flow of Ne and W, as in single-null plasmas, but the stagnation point and divertor retention are less sensitive to ΓNe,puff variations in CDN configurations. Neglecting drifts leads to a substantial overestimation of Ne and W densities near the core boundary. The differing spatial distribution of Ne+ and W+ ionization sources from neutrals leads to distinct ion flux patterns for Ne and W. Importantly, increasing ΓNe,puff can reduce W core leakage.