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Cathode Surface Imaging and Electron Beam Emittance Measurement

Emittance is an important figure of merit for electron beams which, coupled with overall current, determines a beam's utility in vacuum electronic devices (VEDs)1. As VEDs push into higher frequency and higher power regimes, low emittance, high current beams become critical2. Much theoretical work on understanding and predicting emittance has been presented, but little to no experimental results are available1,3,4, We report here the measurement of 2D emittance maps for a series of field emission fiber cathodes and their correlation to surface features, imaged using a field emission electron microscope and scanning electron microscope. This work serves to further inform theoretical investigations into emittance and aid in the a priori selection of suitable cathodes for specific uses.