Comprehensive Gyrokinetic Study of Eigenstate Transitions in Fast Ion-Driven Electrostatic Drift Instabilities

Abstract

This study comprehensively investigates fast ion-driven drift instability, extending the theory in [B. J. Kang and T. S. Hahm, Phys. Plasmas 26, 042501 (2019)]. The eigenmode equation, including the resonant contribution of passing fast ions, is derived and solved using the shooting method. Passing fast ions significantly affect the instability in weak negative shear or moderate positive shear plasmas. Eigenstate transitions to non-ground states occur more readily in weak magnetic shear, high safety factor, and long wavelength perturbations. Linear gyrokinetic simulations using the GKV code verify the theory, showing good agreement with shooting method results. The estimated quasilinear transport indicates that the net energy flux can be inward, without contradicting the second law of thermodynamics. These findings have important implications for heating efficiency and plasma confinement in the heating process, such as Ion Cyclotron Resonance Heating (ICRH) in future fusion devices.

38 pages, 24 figures

References in corpus (4)

• New high-confinement regime with fast ions in the core of fusion plasmas
• A New Paradigm for Turbulent Transport Across a Steep Gradient in Toroidal Plasmas
• On scattering and damping of Toroidal Alfven eigenmode by drift wave turbulence
• Energy exchange between electrons and ions in ion temperature gradient turbulence