Modeling the effects of wall particle recycling on divertor detachment and upstream SOL density flattening in HL-2A by SOLPS-ITER

Abstract This work employs the SOLPS-ITER code package to investigate the impact of wall particle recycling (WPR) on diverter detachment and upstream scrape-off layer (SOL) density flattening in the HL-2 A with a long-leg closed diverter. The results demonstrate that increasing WPR enhances upstream SOL plasma density, facilitating detachment in the HL-2 A closed diverter by increasing target plasma density, neutral density and radiation loss. In contrast, WPR minimally affects the relatively open diverter, primarily due to its weaker detachment capability. Besides, in this study, we demonstrate that WPR can significantly contribute to upstream density flattening, thereby facilitating the suppression of larger edge localized modes in both closed and open diverter configurations. However, the physical mechanisms governing the flattening upstream SOL density differ between the two diverters: the closed diverter upstream SOL density flattening, reducing pedestal radial density gradient mainly through reverse parallel flow arising from a strong ionization source in closed diverter region, while the open diverter upstream SOL density flattening by diverter region recycling neutral particle reflecting due to the weak recycling particle trapping capability.