Abstract
Linear and nonlinear particle-magnetohydrodynamic (MHD) simulation codes are developed to study interactions between energetic ions and MHD modes. Energetic alpha particles with the slowing-down distribution are considered and the behavior of n=2 toroidal Alfvén eigenmodes (TAE modes) is investigated with the parameters pertinent to the present large tokamaks. The linear simulation reveals the resonance condition between alpha particles and TAE mode. In the nonlinear simulation, two n=2 TAE modes are destabilized and alpha particle losses induced thereby are observed. Counterpassing particles are lost when they cross the passing-trapped boundary. They are the major part of lost particles, but trapped particles are also lost appreciably.
Highlights
Compared with previous works4,5 where magnetic moments of alpha particles are set to be zero, the present work has an advantage that a more realistic alpha-particle distribution can be considered
The resonance condition is important to understanding alpha-particle losses in the nonlinear simulation
Alpha particles are lost by TAE modes in the nonlinear simulation
Summary
Component, while the background plasma is described by the full MHD equations which are solved by a finite difference method. The mechanism of alpha-particle losses induced by a single TAE mode was investigated by a Monte. They found that crossing the passing-trapped boundary is a dominant process of the alphaparticle loss induced by a single mode. Theoretical and computational studies have shown that wave trapping of resonant particles works as a saturation mechanism of a single TAE mode. It is, not clear that the wave–particle trapping works as the dominant saturation mechanism when a large number of TAE modes are destabilized. 10 and 11, survive as potential candidates for saturation mechanism This gives us a sufficient motivation to develop a simulation code with nonlinear MHD equations. The particle simulation method is used for the alpha-particle a!
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