Cs halide photocathode for multi-electron-beam pattern generator

摘要

A unique approach to photocathode operation is described in this article. We utilize a relatively large bandgap CsBr photocathode material that under normal conditions would not photoemit with radiation energy less than the bandgap plus the work function. However, the material can be activated by proper UV illumination to obtain photoemission at wavelengths as long as 532 nm. Photoyields as high as several hundred nA/mW and current densities greater than 100 A/cm~2 have been routinely obtained with lifetimes (50% degradation) well in excess of 200 h at 257 nm. The performance of the photocathode meeting all the requirements for a multi-electron-beam pattern generator will be presented.