2D PIC modeling of the helical scrape-off layer current driven by hybrid divertor biased targets in tokamak plasmas

Abstract

The heat flux control of the divertor plate via strike-point splitting generated by biased targets was proposed in the HL-2A tokamak (Cui et al 2021 Fusion Eng. Des. 173 112963). To understand the helical scrape-off layer (SOL) currents driven by hybrid biasing, two SOL current models (model A and B) are employed. Model A is a simplified 2D model that focuses on investigating the effect of biasing on the sheath and elucidating the fundamental physical mechanism of bias-driven SOL current paths. The potential, charge density, electric field and current densities are calculated. Model B takes into account the actual tokamak geometry and computes the resonant magnetic perturbations (RMPs) generated by bias-driven linear decay currents. Additionally, strike-point splitting is observed in the HL-2A tokamak, indicating that the SOL currents generated by hybrid biasing are capable of generating strong RMPs and consequently influence the magnetic topology. These results confirm the potential of heat/particle flux control by hybrid divertor biased targets.

Keywords

• scrape-off layer
• heat flux control
• biased target
• RMP system
• particle-in-cell