The modeling and simulation of field emission array tips using the gun code algorithm in MICHELLE

We report on the incorporation of a model of field emitters (FE) in the MICHELLE Particle-In-Cell (PIC) beam optics code. The FE model is based on a Point Charge Model (PCM) and allows for rapid and analytical representations of tip current, variation, and emission statistics. Its usage enables determining the impact of emission variation on current characteristics and emittance. Rather than cold field emission characterized by the Fowler Nordheim (FN) equation, a General Thermal-Field (GTF) emission model treats warm and hot field emission sources. We discuss convergence characteristics and use of such models in the steady-state gun code algorithm. Specifically, we look at the rate of convergence, ramifications of meshing techniques including unstructured and structured conformal meshes and different field emission tip geometries.