Work

Global gyrokinetic particle simulation of kinetic ballooning modes with energetic ions

Year: 2025

Type: article

Abstract: Interactions between energetic ions (EIs) and kinetic ballooning modes (KBMs) are inevitable in fusion reactors characterized by high- β plasmas with a large population of alpha particles ( β h ∼ β e , i , where β h , e , i = 2 μ 0 p h , e , i / B 0 2 ). In this work, the effects of EIs on KBM stability are investigated using first-principles gyrokinetic simulations, which demonstrate the roles of magnetohydrodynamic (MHD) ballooning-interchange drive, wave–particle resonance and orbital effects in several parameter regimes of practical interest. In particular, it is found that EI–KBM interactions are mostly determined by three dimensionless parameters: the EI–thermal electron temperature ratio T h / T e , the KBM perpendicular wave vector normalized by EI orbit width k θ ρ d and the EI pressure ratio β h , which are associated with resonance condition, finite orbit width (FOW) screening and EI drive strength for Alfvénic modes. For typical orderings of T h / T e ≫ 1 and β h ∼ β e , i , k θ ρ d becomes crucial for relevant physical processes. (i) In the short-wavelength regime of k θ ρ d ≫ 1 , the response of EIs to KBM electromagnetic fluctuations is greatly reduced due to strong FOW screening, which leads to a weakly stabilizing effect on KBMs via thermal ion dilution, despite the large β h . (ii) In the long-wavelength regime of

Source: Nuclear Fusion

DOI: 10.1088/1741-4326/ae27e3