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Impurity injection is an effective way to control the burst of edge localized modes (ELMs), which have to be avoided due to the severe damages on the plasma-facing components in future fusion reactor. In recent EAST experiments, it has been demonstrated that, large ELMs can be mitigated or even suppressed by neon (Ne) seeding utilizing supersonic molecular beam injection (SMBI) when the Ne density reaches a certain level in the pedestal region. Cao et al. [Plasma Sci. Technol. 27 (2025) 115105] have attributed the ELM suppression to the open of particle transport channel. In this work, to investigate the underlying mechanism on the enhanced particle transport due to the Ne injection via SMBI, simulations are performed using the CLT (Ci-Liu-Ti, the Chinese name of the magnetohydrodynamics (MHD)) code.
CLT code is widely adopted to study the MHD instabilities such as tearing modes, kink modes and so on. For investigating the pedestal instabilities, the ion diamagnetic drift effect is included in the physical model. Furthermore, to simulate the process of Ne SMBI injection, an impurity injection module is developed. Based on the EAST-like equilibrium generated by the high-accuracy free-boundary equilibrium solver CLT-EQ (CLT-EQuilirium), the CLT simulations are performed with the Ne injection from the outer mid-plane. It is found that, due to the Ne injection, a n = 1 mode can be triggered in the pedestal region, which leads a significant enhancement of the plasma transport. The pressure gradient and current density in the pedestal region are thus reduced, causing a reduction of ELM size by around 30%. The n = 1 mode is considered as the tearing mode according to the analysis of the magnetic structure and drift frequency. By scanning the Ne injection flux, it’s found that ELMs can be mitigated when the maximum Ne concentration in the pedestal region reaches ~5%. In summary, the results of CLT simulations are qualitatively consistent with the EAST experimental observation with Ne SMBI injection, and the enhancement of plasma transport and further mitigation of ELMs could be attributed to the trigger of the n = 1 tearing mode in the pedestal region due to impurity injection.