Evaluation of ideal MHD mode stability of CFETR baseline scenario

TL;DR

This study evaluates the stability of ideal MHD modes in the CFETR baseline scenario, showing that edge-localized modes are unstable but do not threaten core stability, supporting steady-state operation if ELMs are controlled.

Contribution

It provides a detailed stability analysis of the CFETR baseline scenario using NIMROD and AEGIS codes, highlighting the edge-localized nature of instabilities and the effects of wall position.

Findings

Modes are edge localized and unstable in ideal MHD.

Growth rates increase with wall proximity until saturation.

No dominant global core modes are identified.

Abstract

The CFETR baseline scenario is based on a H-mode equilibrium with high pedestal and highly peaked edge bootstrap current, along with strong reverse shear in safety factor profile. The stability of ideal MHD modes for the CFETR baseline scenario has been evaluated using NIMROD and AEGIS codes. The toroidal mode numbers (n=1-10) are considered in this analysis for different positions of perfectly conducting wall in order to estimate the ideal wall effect on the stability of ideal MHD modes for physics and engineering designs of CFETR. Although, the modes (n=1-10) are found to be unstable in ideal MHD, the structure of all modes is edge localized. Growth rates of all modes are found to be increasing initially with wall position before they reach ideal wall saturation limit (no wall limit). No global core modes are found to be dominantly unstable in our analysis. The design of $q_{min}>2$ and strong reverse shear in $q$ profile is expected to prevent the excitation of global modes. Therefore, this baseline scenario is considered to be suitable for supporting long time steady state discharge in context of ideal MHD physics, if ELMs could be controlled.