Theoretical model of the intrinsic emittance of a photocathode

摘要

A theoretical expression for the intrinsic emittance of a photocathode is developed based on a method of evaluating moments of the emission distribution function. The method is first used to reevaluate the well-known rms emittance of a thermionic source, and then, using analogous approximations but with an updated theoretical model of photoemission, an equation for the intrinsic emittance and brightness of a photocathode of comparable simplicity to the thermionic case is obtained in the limit of weak field and low temperature.