Space-charge-limited emission models for particle simulation

Summary form only given. Space-charge-limited (SCL) emission of electrons from various materials is a common method of generating the high current beams required to drive high power microwave (HPM) sources. In the SCL emission process, sufficient space charge is extracted from a surface, often of complicated geometry, to drive the electric field normal to the surface close to zero. The emitted current is highly dominated by space charge effects as well as ambient fields near the surface. Simulation has become an important element in the design and analysis of HPM sources. In this work, we consider a number of computational models for the macroscopic SCL emission process. In particular, we consider models including application of Gauss´s law and the Child-Langmuir law for space charge limited emission. The work includes consideration of enhancement of current near edges in SCL emitters. Models are described for ideal conductors, lossy conductors, and dielectrics. Also considered is the discretization of these models, and the implications for the emission physics. Previous work on primary and dual-cell emission models is re-examined, and aspects of the performance including fidelity and noise properties are improved. Models for one-dimensional diodes are considered, as well as multidimensional emitting surfaces which include corners and transverse fields. Both electrostatic and electromagnetic limits are considered.