A novel model for analyzing singularities induced by curved PMLs in ICRF coupling simulations and its application to J-TEXT antenna design

In simulations of ion cyclotron wave coupling between antennas and edge plasma, curved models more accurately capture structural details such as the antenna geometry, leading to results that better reflect realistic conditions. While implementing curved perfectly matched layers (PMLs) in such models, we observed that electric field singularities may arise under certain conditions. To better understand the origin of these singularities, their impact on PML performance, and potential mitigation strategies, we developed an idealized model that is amenable to theoretical analysis. Based on this model, a set of curved PML parameters was obtained that can balance effective wave absorption and the mitigation of field singularities, while further refinement remains necessary in practical applications. Using these parameters, 2D curved antenna–plasma coupling models were constructed to further optimize the PML configuration under the J-TEXT scenario. The refined parameters were then applied in 3D curved models. Meanwhile, conventional planar PML techniques were used to build corresponding 2D and 3D planar antenna–plasma coupling models, and differences between the planar and curved models were assessed. Coupling impedance is used as a performance metric to guide the design of the ICRF antenna for the J-TEXT device. A significant discrepancy in coupling impedance is observed between the 3D planar and curved models, which is attributed to differences in antenna structures, leading to variations in the surface current distribution on the strap and the spatial distribution of the local electric field. These findings underscore the importance of accurately reconstructing antenna geometry for reliable coupling evaluations.