Speaker
Description
Fast-ion transport in EAST plasmas is studied using a particle-tracing method for two cases: edge-localized-mode (ELM) electromagnetic perturbations alone and coexisting ELM and tearing-mode (TM) perturbations. The ELM perturbations are obtained from nonlinear BOUT++ simulations first and then mapped onto the triangular equilibrium mesh used in the Particle orbit Tracing Code (PTC). When ELM perturbations alone are considered, the total fast-ion loss fraction increases only slightly, by approximately 0.7% of the total fast-ion loss compared with the unperturbed case. Nevertheless, clear fast-ion acceleration is observed in the simulations, supporting the contribution of the parallel component of the ELM-induced electric field to the acceleration process. The resulting ELM-induced transport is localized near the plasma boundary around the inner and outer midplanes, and the toroidal deposition exhibits filament-like structures. For the coexisting TM and ELM perturbations, the threshold for TM-induced orbit stochasticity remains barely changed, while the loss characteristics depend on the TM perturbation amplitude. This amplitude dependence is manifested in two regimes: near the TM-determined stochastic threshold, ELM perturbations moderately increase the total number of lost fast ions but nearly double their local deposition density; at larger TM amplitudes, the small drift-island chains generated by TM-ELM synergy, which can already appear near the stochastic threshold, become sufficiently effective to offset ELM-enhanced edge losses, leading to a reduction in the total fast-ion loss.