Numerical analyses of energetic particles in LHD

The confinement of energetic ions generated by neutral beam injection (NBI) and ion cyclotron resonance frequency heating is studied using GNET simulation code, in which the drift kinetic equation is solved in fivedimensional phase-space. The steady-state distributions of the energetic ions are obtained, and characteristics of the energetic-ion distribution depending on the plasma heating method are shown. The magnetic configuration effect on the energetic-ion confinement is also investigated, and it is found that the energetic-ion confinement is improved by a strong inward shift of the magnetic axis position in the major radius direction. The interaction between energetic particles and Alfvén eigenmodes are investigated using the MEGA code and the AE3D code. A reduced version of the MEGA code has been developed to simulate the Alfvén eigenmode (AE) evolution in the Large Helical Device (LHD) plasma with NBI and collisions taken into account. The spatial profile and frequency of the AE modes in the LHD plasma are analyzed with the AE3D code. The evolution of energetic particles and AE mode amplitude and phase are followed in a self-consistent way, while the AE spatial profiles are assumed to be constant. It is demonstrated that the AE bursts can be simulated with the new code.