Stabilizing effect of enhanced resistivity on peeling-ballooning instabilities on EAST

TL;DR

This study investigates how increased resistivity, caused by higher impurity levels, can stabilize peeling-ballooning instabilities in EAST tokamak plasmas, extending previous findings from NSTX and providing insights into impurity effects on pedestal stability.

Contribution

It extends the understanding of resistivity's stabilizing effect from low-n modes to intermediate-n peeling-ballooning instabilities in EAST using linear stability analysis.

Findings

Resistivity stabilizes PB instabilities in EAST, but less effectively than in NSTX.

Impurity-induced resistivity has a beneficial effect on pedestal stability.

Physical mechanisms behind impurity effects are better understood through this analysis.

Abstract

Previous stability analysis of NSTX equilibrium with lithium-conditioning demonstrates that the enhanced resistivity due to the increased effective charge number Zeff (i.e. increased impurity level) can provide a stabilizing effect on low-n edge localized modes (Banerjee et al 2017 Nucl. Fusion 24 054501). This paper extends the resistivity stabilizing effect to the intermediate-n peeling-ballooning (PB) instabilities with the linear stability analysis of EAST high-confinement mode equilibria in NIMROD two-fluid calculations. However, the resistivity stabilizing effect on PB instabilities in the EAST tokamak appears weaker than that found in NSTX. This work may give better insight into the physical mechanism behind the beneficial effects of impurity on the pedestal stability.