The effect of a non-uniform on ripple-trapped neutral beam ions is investigated using both the Monte Carlo method and Fokker-Planck approach. The increase in the neutral particle flux from ripple-trapped ions observed by the CX detector at an L-H transition in the ASDEX Upgrade tokamak is reproduced in both simulations by turning on near the plasma periphery.
Heikkinen, J., Kurki-Suonio, T., & Herrmann, W. (1998). Ripple-trapped beam ions in the presence of a radial electric field. Plasma Physics and Controlled Fusion, 40(5), 679-682. https://doi.org/10.1088/0741-3335/40/5/022