Effect of resonant magnetic perturbations with plasma response on particle orbit characters

Abstract

The ion orbits considering the resonant magnetic perturbation (RMP) fields with plasma response are studied numerically using the full orbit code based on HL-2A tokamak parameters. The results show that RMP with plasma response can cause a more significant radial orbit expansion than the vacuum RMP field. Further study exhibits that the physical mechanism of the orbit expansion relates to the resonant field amplification (RFA) effect. The passing orbits expansion become quite large when ions pass through the region where the perturbed field is strongly amplified. Meanwhile, the trapped orbits expansion is determined by the average value of the perturbed field where corressponding orbit goes by. This indicates that the plasma response to RMP plays an important role in changing the characteristics of ion orbits, which can lead to a redistribution of fast ions and thus providing a possible mechanism for the degradation of plasma confinements in experiments.