Numerical simulation of impact of supersonic molecular beam injection on edge localized modes

A three-field model with the impact of supersonic molecular beam injection (SMBI) based on the BOUT++ code is built to simulate edge localized modes (ELMs). Different parameters of SMBI are explored to find an optimal SMBI scenario for ELM mitigation. The linear simulations show that the growth rate of peeling-ballooning mode is reduced by SMBI. The reduction amplitude of the growth rate is increased when the amplitude or width of SMBI is increased, and when SMBI is deposited at the top, bottom and middle of the pedestal, the reduction amplitude increases successively. The nonlinear simulations show that the ELM size is reduced by SMBI. The reduction amplitude of the ELM size is increased when the amplitude or width of SMBI is increased, and when SMBI is deposited at the bottom, top and middle of the pedestal, the reduction amplitude increases successively. Surface-averaged pressure profiles and filamentary structures are analyzed when the ELMs erupt. Deep deposition of SMBI such as at the top and middle of the pedestal reduces the inward collapse amplitude of the pressure profiles, which can improve the confinement efficiency during ELMs. Shallow deposition of SMBI such as at the middle and bottom of the pedestal reduces the outer extent of the filamentary structures, which can slow down the erosion of plasma-facing components caused by ELMs. In conclusion, shallow deposition of SMBI with sufficient amplitude and width can meet the needs of ELM mitigation.