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

The heat flux control of the divertor plate via strike-point splitting generated by biased targets was proposed in the HL-2A tokamak [Cui B.T. et al 2021 Fusion Eng. Des. 173 112963]. To understand the physical mechanism of bias-driven scrape-off layer (SOL) currents, the electromagnetic particle-in-cell (PIC) code is employed to calculate the potential, charge density, electric field and current densities for different angle between the wall and magnetic field. Results suggest that the hybrid biasing can drive the electron current that decays along the magnetic field line, and the ion current that is perpendicular to the magnetic field line. A strong local electric field E, which can induce an E×B drift, is generated near the biased target plates. Moreover, the bias-driven parallel currents produce three-dimensional (3D) field perturbations. Both mechanisms — the E×B drift and the 3D magnetic field generation affect the heat flux at the same time. These modeling results confirm the potential of heat flux control by hybrid divertor biased targets.