Geometry and Material Effects on Electron Transport in Hop Funnels

Electron hop funnels have shown the potential to allow the use of field emission arrays in microwave vacuum electron devices. Hop funnels enhance the performance of field emission arrays by increasing the uniformity and current density and by providing protection from ion back bombardment. This work investigates how different hop funnel materials and geometries affect the performance of the hop funnel. Funnels have been constructed out of MACOR and alumina each with three different funnel angles. The current to voltage characteristic of these funnels and the energy of electrons transmitted through the funnel have been measured. In addition to the experimental work, this thesis focused on benchmarking the new version of the particle trajectory software, Lorentz 2E v9.2, used for this research. The software has been tested and confirmed to reproduce the results from previous work. After the software was tested, the models from previous work were modified to simulate the electron hop funnels used in the experimental work of this thesis. Some of the hop funnels from this work have been simulated. The experimental and simulation results will be presented. The experimental work of this thesis found that MACOR and alumina hop funnels exhibit very similar behavior, but some distinctions can be found between the performance of different hop funnels angles. In addition, it will be shown that simulation does not correctly model all of the electron hop funnels. This work has enhanced the electron hop funnel research by refining the simulation model and experiment work