Development and Application of Emission Models in the MICHELLE Beam Optics Simulation Code

Abstract

We present new advances in the MICHELLE charged particle beam optics code in area of advancing emission models and algorithms that capture more electron emission physics. The new capability covered in this paper concerns the implementation of a new general thermal field (GTF) model that predicts current density in the transition region between temperature limited emission and field emission. In the case of electron thermionic emission where the effective AK gap is not large compared with the potential minimum distance that forms in front of the cathode, we employed a modified and improved thermionic emission model Coupled to these models are a new thermal beam model that better control macro-particle count while maintaining simulation fidelity, as well as new meshing methodologies that improve emission fidelity in the regime of disparate spatial scales, especially useful for field emitter fibers. Lastly, also for field emission fibers, we will present results from the implementation of a self-consistent thermal model. To support such widely ranging spatial scales, effort has been put into disparate meshing capabilities. The presentation provides an overview of the new capabilities that has been achieved.