Determination of the Field Enhancement Factor on Photocathode Surface via the Schottky Effect

Using photon energy that is less than the work function, we employ the Schotty effect to determine the field-enhancement factor on the surface of a Mg photocathode. The Schottky effect is manifested via a shift in the threshold for photoemission as the amplitude of the RF in the photoinjector gun is varied. From the threshold condition, we can directly determine the field enhancement factor on the cathode surface. This is a viable technique to obtain the field enhancement factor of surfaces of other materials such as Nb and Cu.