RF density-modulated electron source simulations with MICHELLE

Summary form only given. New models have been developed and implemented in the MICHELLE Finite-Element Electrostatic Particle-in-Cell code¹ in support of modeling RF photocathodes and IOTs (inductive output tubes). In the case of photocatodes, low emittance, high current density sources are required to achieve the small beam size needed for high frequency vacuum electronic devices and, in particular, low emittance sources are demanded for high power free electron lasers (FELs). Emission models are of particular importance in the emittance-dominated regime, where emission non-uniformity and surface structure of the cathode can have an impact on beam characteristics and situations that depend on beam quality (e.g., halo). We have been developing comprehensive time-dependent photoemission models that account for laser and cathode material and surface characteristics and adapting them to develop emission models for inclusion into beam simulation codes². In addition to the photoemission effects, including the effects of thermal field emission and modeling dark current are key to predicting beam quality and performance degradation due to beam tails and halo.