Dynamics of ion temperature gradient modes in burning plasma conditions in the presence of energetic particles

TL;DR

This study investigates how energetic particles influence ion temperature gradient modes in burning plasma conditions, revealing stabilization mechanisms and their dependence on particle distribution and plasma parameters, crucial for future fusion devices like ITER.

Contribution

It extends previous analyses of EP-ITG interactions to broader EP temperature ranges and distribution functions, providing new insights into stabilization mechanisms in burning plasma regimes.

Findings

DDRM effective at intermediate EP temperatures

Dilution effect dominates in burning plasma regime

EP stabilization weaker than β-stabilization in ITER scenario

Abstract

The interaction between energetic particles (EPs) and ion temperature gradient (ITG) modes is studied using the global particle in cell ORB5 code. In this work, we extend previous studies to a broader range of EP temperatures, including the burning plasma regime and to wider variety of EP distribution functions. Two main stabilization mechanisms are found to be effective in ITG stabilization confirming previous studies: direct dispersion relation modification (DDRM) effective only at intermediate EP temperatures and dilution effect (DE) which is independent of EP temperature and becomes dominant in burning plasma regime ($T_f > 50T_i$). The study is further extended to slowing-down EP distributions which in contrast exhibit no DDRM-related stabilization. The findings are further validated in an ITER pre-fusion operation scenario and additionally compared with electromagnetic effects. In this scenario EP stabilization is found to be weaker than $\beta$-stabilization. Overall, these results provide better understanding of EP-ITG interactions over a wider range of EP parameters relevant to burning plasma regime which is important for predicting turbulence and confinement in future devices such as ITER.