Fast-ion losses due to externally applied static magnetic perturbations in the Large Helical Device

In this study, using a scintillator-based lost fast-ion probe, we have measured fast-ion losses in the Large Helical Device, in which the losses were caused by externally applied static magnetic perturbations (MPs) having small amplitudes. Energy and pitch-angle resolved measurements reveal that the effects of MPs on fast-ion losses occur in both high and low pitch-angle regions. A Lorentz orbit-following calculation indicates that static MPs can change the orbits of fast ions, which can enhance the transport/loss of fast ions. (author)