Stable edge localized mode suppression by Ne-supersonic molecular beam injection on EAST

In the 2018 EAST (Experimental Advanced Superconducting Tokamak) experiments, type-I ELMs (edge localized modes) were mitigated and suppressed by Ne-SMBI (supersonic molecular beam injection) injection during H-mode discharges. No energy confinement degradation was observed during ELM suppression, whereas approximately 10% degradation was observed during ELM mitigation. The observation of broadband MHD (magnetohydrodynamic) turbulence during ELM suppression indicates it may be the primary particle transport channel. The electron density profile in the pedestal top increased and the edge radiation increased with Ne-SMBI injection, which could reduce heat fluxes reaching the divertor. Pedestal profile changes appear adequate to trigger small transport events and mitigate large ELMs. In the 2022 EAST experimental campaign, stable 2 s ELM suppression was achieved by adjusting the Ne-SMBI injection rate. High-frequency coherent modes around 250 kHz, possibly corresponding to micro-tearing modes (MTM), appeared during ELM suppression. In addition to impurity SMBI injection, fuel particle D₂-SMBI injection was also applied for ELM mitigation. Experimental results show D₂-SMBI has small impact on the edge, increasing ELM frequency without significant ELM mitigation compared to impurity SMBI.