MHD stability analysis of ideal wall modes for CFETR upgrade phase-I scenario using NIMROD

TL;DR

This study evaluates the ideal MHD stability of CFETR upgrade phase-I using NIMROD, revealing all modes are unstable with edge-localized characteristics and highlighting the importance of two-fluid models for high-n modes.

Contribution

First comprehensive MHD stability analysis of CFETR upgrade phase-I using NIMROD, comparing single-fluid and two-fluid models across a range of mode numbers.

Findings

All modes are unstable with edge-localized features.

Two-fluid MHD models predict higher growth rates for high-n modes.

Increasing wall position enhances instability of low-n modes.

Abstract

Ideal MHD stability of China Fusion Engineering Test Reactor (CFETR) upgrade phase-I baseline scenario has been evaluated using the initial value code NIMROD. The toroidal mode numbers for n=1-30 have been considered for stability analysis both in single-fluid and two-fluid MHD models. Our calculation rusults show that all modes are found to be unstable with characteristics of edge-localized modes. For n $\leq$ 13 modes, two-fluid MHD model gives a slightly higher growth rates than single-fluid MHD model, while for n $>$ 13 modes, this trend becomes opposite, which means two-fluid MHD model is needed for high-n mode analysis. In addition, $n=1-10$ modes are found to be more unstable with increasing wall position and eventually their growth rates approach values in the no-wall limit.