Ring-cusp discharges use multiple permanent magnet rings to facilitate confinement of the high energy electrons and other plasma species. The magnetic field configuration consists of converging fields toward the magnetic cusps with a large ratio of the maximum to the minimum magnetic field strength. In such configurations, a plasma fluid simulation with a regular mesh can lead to undesirable numerical diffusion errors caused by the anisotropicity of plasma and the misalignment of the grid with the field. In this paper, details of a custom technique for magnetic field aligned (MFA) mesh generation are provided. The MFA meshes may consist of irregular nodes that are attached to more than four mesh elements. The numerical method developed here can be applied to such meshes to solve the plasma diffusion equation. The combination of the MFA mesh generation and the numerical method is applied to two test cases: perfectly anisotropic plasma in a single cusp configuration and moderately anisotropic plasma in a ring-cusp discharge-like configuration. It is shown that a simulation with the MFA mesh can provide a more accurate solution compared with the regular mesh with a similar number of mesh elements. However, realizing the inherent benefits of the MFA mesh often requires improvements on the mesh quality near the boundary, in particular, the smoothness of the near-boundary elements.
展开▼
