Low-$n$ global ideal MHD instabilities in CFETR baseline scenario

TL;DR

This study evaluates the linear ideal MHD stability of the CFETR baseline scenario, analyzing low-$n$ instabilities with two codes, and finds the $n=1$ resistive wall mode can be stabilized by plasma rotation.

Contribution

It provides a comprehensive stability analysis of CFETR baseline scenario using NIMROD and AEGIS, including effects of wall shape and plasma-vacuum profiles, and assesses RWM stabilization.

Findings

Good agreement between NIMROD and AEGIS in growth rates for $n=1-10$ modes.

Higher-$n$ modes are ballooning and localized; lower-$n$ modes have kink components.

The $n=1$ RWM can be stabilized by plasma rotation above 2.9 extbackslash% of core Alfvén speed.

Abstract

This article reports an evaluation on the linear ideal magnetohydrodynamic (MHD) stability of the China Fusion Engineering Test Reactor (CFETR) baseline scenario for various first-wall locations. The initial-value code NIMROD and eigen-value code AEGIS are employed in this analysis. A good agreement is achieved between two codes in the growth rates of $n=1-10$ ideal MHD modes for various locations of the perfect conducting first-wall. The higher-$n$ modes are dominated by ballooning modes and localized in the pedestal region, while the lower-$n$ modes have more prominent external kink components and broader mode profiles. The influences of plasma-vacuum profile and wall shape are also examined using NIMROD. In presence of resistive wall, the low-$n$ ideal MHD instabilities are further studied using AEGIS. For the designed first-wall location, the $n = 1$ resistive wall mode (RWM) is found unstable, which could be fully stabilized by uniform toroidal rotation above 2.9\% core Alfv\'en speed.