Photocathode Quantum Efficiency Mapping at High Resolution Using a Digital Micromirror Device

An electron beam’s quality is fundamentally limited by its attributes at the cathode. The emission from photocathodes can be bright, but not necessarily uniform. Quantum efficiency (QE) maps generated by selectively illuminating the cathode surface reveal this nonuniformity. In this paper a proof-of-principle experiment is described in which a high resolution map of the QE is generated using a digital micromirror device. We show a substantial improvement over the best results reported for laser raster scanning.