Stabilizing effects of resistivity on low-n edge localized modes in NSTX

TL;DR

This paper demonstrates that increased edge resistivity, influenced by Lithium-conditioning, stabilizes low-n ELMs in NSTX, highlighting the importance of two-fluid effects in ELM suppression.

Contribution

It reveals the stabilizing role of enhanced edge resistivity due to Lithium-conditioning in suppressing low-n ELMs, emphasizing the significance of two-fluid effects in the MHD model.

Findings

Enhanced resistivity contributes to ELM stabilization.

Lithium-conditioning increases Z_eff, affecting resistivity.

Two-fluid effects are crucial for the stabilizing mechanism.

Abstract

The stabilizing effects of enhanced edge resistivity on the low-n edge localized modes (ELMs) are reported for the first time in the context of ELM suppression in H-mode discharge due to Lithium-conditioning in the National Spherical Torus Experiment (NSTX). Here n is the toroidal mode number. Linear stability analysis of the corresponding experimental equilibrium suggests that the change in the equilibrium plasma density profile alone due to Lithium-conditioning may be insufficient for a complete suppression of ELMs. The enhanced resistivity due to the increased effective electric charge number Z eff after Lithium-conditioning can account for additional stabi- lization effect necessary for full ELM suppression. Remarkably, such a stabilizing effect of enhanced edge resistivity on the low-n ELMs only exists when two-fluid effects are considered in the MHD model.