Fast-ion loss simulation with MEGA code in the Large Helical Device

The evaluation of fast-ion confinement is indispensable for the prediction of the heating efficiency in fusion reactor. The fast-ion confinement depends not only on the collisional transport but also on the fast-ion driven magnetohydrodynamics (MHD) instabilities such as Alfvén eigenmodes (AEs) which induce the fast-ion transport and losses. Therefore, it is an important issue to identify the fast-ion driven MHD instabilities and clarify the lost fast-ion distribution due to the instabilities. In the Large Helical Device (LHD), which is one of the largest heliotron/stellarator devices with non- axisymmetric three-dimensional magnetic configuration, the fast-ion driven MHD instabilities such as the toroidal Alfvén eigenmodes (TAEs) were observed. In addition, the AE-induced fast-ion losses were measured by a scintillator-based fast-ion loss detector (FILD)[2]. The relationship between the amplitude of the instabilities and the fast-ion losses are investigated.