Recent advances in the MICHELLE 2D/3D electron gun and collector modeling code

Summary form only given. The MICHELLE code is a new finite-element (FE) two-dimensional (2D) and three-dimensional (3D) electrostatic particle-in-cell (PIC) code that has been designed to address the recent beam optics modeling and simulation requirements for vacuum electron devices, ion sources, and charged-particle transport. Problem classes specifically targeted include depressed collectors, gridded-guns, multi-beam guns, sheet-beam guns, and ion thrusters. The focus of the development program is to combine modern finite-element techniques with improved physics models. The code employs a conformal mesh, including both structured and unstructured mesh architectures for meshing flexibility, along with a new method for accurate, efficient particle tracking. Particle emission models for thermionic beam representation are included that support primary emission and secondary emission. Secondary emission is handled with an advanced model. Also, new ion source plasma conditions and charge exchange models are included. This presentation focuses on two significant advances to MICHELLE over the past year; hybrid structured/unstructured mesh support, and a time-domain electrostatic algorithm. The hybrid structured/unstructured mesh support enables MICHELLE to use the most-appropriate meshing geometry for the task. Smooth, structured meshes are ideal for tracking particles through regions with simply geometries. Unstructured meshes are ideal for meshing complicated geometries, and more readily supports adaptive mesh refinement. In regions where the mesh is represented by smooth, relatively uniform meshes, the particle tracking has reduced numerical noise. However, complicated geometries can be intractable to generate a mesh for using structured meshes.