Electron Hop Funnel Measurement and Simulation for Various Geometries and Materials

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Conference Proceeding

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Vacuum electron hop funnel devices can be used to collect and spatially average electron emission current from field emission arrays (FEAs). At the proper operating voltage the funnels provide unity gain of the injected emission current. The resulting beams can be more uniform than from typical FEAs, and the funnel technique might be used to generate very uniform electron sheet beams. In the work described here, hop funnels have been fabricated from low temperature co-fired ceramic (LTCC). Other materials will also be tested including SiO2 and Macor in order to measure and simulate the effect that different secondary emission yield curves has on the insulating surface charge distribution and I-V characteristics. For each insulating material, hop funnel structures with varying wall slopes will be constructed to measure the relationship of the slope of the hop funnel wall with the "knee" of the I-V curve. In addition, the electron energy distribution of the hop funnel electron beam, as well as the beam spread, will be measured for each material and wall slope to create a matrix of data which will be used to determine an optimal hop funnel structure for a minimal average transverse electron energy component of the exit beam. The data will be compared against the predictions of the particle trajectory computer simulation Lorentz and will be used to refine the statistical parameters in the numerical simulation. Based on the results, a novel slit design will be constructed of LTCC to be used with the FEAs to generate an electron sheet beam.