Emittance of a photocathode: Effects of temperature and field

Abstract

The emittance of a photocathode is evaluated using a distribution function ("Moments") approach to calculate the moments of the momentum. The effects of temperature and field, which affect the electron distribution and transmission probability, respectively, of electrons incident on the surface barrier, are found. The resulting formulations of emittance are compared to the asymptotic limit found by D.H. Dowell and J.F. Schmerge, and their formulation is shown to be more generally applicable than the approximations within it would indicate for metals. The methodology is extended to develop an asymptotic emittance estimate for semiconductor photocathodes. © 2010 The American Physical Society.