2021 Volume 16 Pages 2402052
Neutral beam (NB) fast-ion loss mechanisms in the large helical device (LHD) are investigated by the combination of the neutron measurement, the classical slowing-down simulation, and the neo-classical guiding center orbit following simulation. It is found that the neo-classical transport provides little contribution to the loss of tangentially injected NB fast-ions. For perpendicularly injected NB fast-ions, the neo-classical transport has more than 40% contribution to the NB fast ion loss. These results indicate that there are other loss mechanisms dominant in LHD plasmas. The charge exchange loss is one of the plausible candidates for the loss mechanism.