Description
We present Vlasov kinetic simulations of ELM plasma transport from the mid-plane to divertor targets using KOBRA, a code employing adaptive mesh refinement (AMR) and an asymptotic-preserving (AP) scheme for the modified Poisson equation. Two characteristic scales governing numerical stability and computational efficiency are quantitatively analyzed: the Debye sheath length $l_\mathrm{sheath}$ and the timescale $\tau_\mathrm{quasi}$ for ELM plasma to enter the quasi-neutral state. By selectively disabling the electric field solver at different times, we find that after the ELM filament reaches the divertor targets at approximately $7\tau_e$, the self-consistent electric field exerts only a weak influence on ion transport. Ions effectively enter a free-streaming regime by $\sim 10\tau_e$, enabling significant reduction in computational cost by turning off the field solver beyond this point without meaningful loss of accuracy in ion flux predictions. Grid resolution studies at $2\lambda_D$ and $4\lambda_D$ reveal that the sheath length is approximately $2\lambda_D$--$3\lambda_D$, consistent with a classical Debye sheath. Insufficient resolution at $4\lambda_D$ introduces spurious electric field oscillations that propagate into the quasi-neutral region. These results provide quantitative guidance for resolving the sheath and optimizing solver strategies in kinetic ELM simulations.