BEAMS In the literature: open

How surface roughness and work-function patchiness raise intrinsic emittance

In plain words

Real cathode surfaces are bumpy and patchy at the nanometer scale, which deflects electrons as they leave. The size of this effect for real materials is not well quantified.

Precise statement

For a photocathode with measured topography (rms height, correlation length) and work-function variation in an extraction field $E \sim 0.1 \text{ to } 1\,\mathrm{MV}/\mathrm{cm}$, compute the contribution of slope and local transverse fields to MTE, and determine the surface quality needed for MTE below $5\,\mathrm{meV}$.

What would settle it

Calculated MTE from measured surface maps compared with MTE measured on the same cathodes at several extraction fields.

See also