Nonlinear dependence of plasma potential and ion impinging energy on energy loss of edge localized modes

Particle-in-cell (PIC) modelling has been performed to investigate the impact of energy loss during edge localized modes (ELMs) on the plasma potential and ion impinging energy on the divertor target. A double-peak structure of the ion impinging energy has been identified under JET-relevant ELM conditions. The ELM burst leads to a strong increase in the potential drop in front of the target plate, which accelerates the cold ions from the downstream divertor and accordingly causes a peak value of ion impinging energy. Moreover, the great potential drop helps confine the fast electrons and leads to a reduction in the potential drop and ion impinging energy. The arrival of the upstream hot ions results in the second peak value of ion impinging energy. The maximum potential drop and ion impact energy show a linear dependence on the pedestal temperature. Further, a nonlinear dependence of the peak potential drop and ion impact energy on the ELM energy loss can be ascertained based on the PIC simulations.