Use of multiphoton photoelectric process to generate a high brightness electron beam for free-electron lasers

Abstract

This letter describes a photocathode of tungsten driven by a frequency-doubled Nd:YAG laser. In this case, photoelectrons emerged by two-photon photoelectric process. The current density quadratically depended on the incident laser intensity, and the quantum yield then increased linearly with the laser intensity. Furthermore, by heating the cathode, we could improve the quantum yield. At a temperature around 1600 °C, the peak current was measured to be 5.8 A with an irradiation of 3.2 MW, and then the quantum yield was to be 2.4×10−6.