A systematic approach to the linear-stability assessment of Alfv\'en eigenmodes in the presence of fusion-born alpha particles for ITER-like equilibria

TL;DR

This paper presents a systematic, efficient method for assessing the linear stability of Alfvén eigenmodes in ITER-like plasmas, focusing on identifying the most unstable modes influenced by fusion-born alpha particles.

Contribution

It introduces a comprehensive approach combining eigenmode scanning, discretization validation, and interaction evaluation with alpha particles, streamlining stability analysis for fusion scenarios.

Findings

All relevant eigenmodes can be identified efficiently.

The method isolates the most unstable modes for detailed study.

It facilitates scenario planning for ITER and future reactors.

Abstract

A systematic approach to assess the linear stability of Alfv\'en eigenmodes in the presence of fusion-born alpha particles is described. Because experimental results for ITER are not available yet, it is not known beforehand which Alfv\'en eigenmodes will interact more intensively with the alpha-particle population. Therefore, the number of modes that need to be considered in stability assessments becomes quite large and care must be exercised when choosing the numerical tools to work with, which must be fast and efficient. In the presented approach, all possible eigenmodes are first found after intensively scanning a suitable frequency range. Each solution found is then tested to find if its discretization over the radial grid in use is adequate. Finally, the interaction between the identified eigenmodes and the alpha-particle population is evaluated with the drift-kinetic code CASTOR-K, in order to assess their growth rates and hence their linear stability. The described approach enables one to single out the most unstable eigenmodes in a given scenario, which can then be handled with more specialized tools. This selection capability eases the task of evaluating alpha-particle interactions with Alfv\'en eigenmodes, either for ITER scenarios or for any other kind of scenario planning.