Effects of cathode surface roughness on the quality of electron beams

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Abstract
The effects of the roughness of the cathode surface on the emittance of an electron beam are examined. Tentative scaling laws are suggested which yield the bounds on the beam emittance due to surface roughness for both temperature-limited and space-charge-limited regimes. These formulas are found to be consistent with numerical integration of electron trajectories over a wide range of parameters. In general, roughness-induced beam emittance may be reduced by a factor of 2–5, if the cathode is operated in the space-charge-limited regime rather than in the temperature-limited regime.