Triple evaporation growth and photoemission characterization of bialkali antimonide photocathodes

Abstract

The development of high-performance photocathodes is essential for generating high-brightness electron beams required by existing and future accelerators. This work introduces a state-of-the-art triple evaporation growth system designed for bialkali antimonide photocathodes. By enabling the simultaneous deposition of all three materials, this system significantly enhances vacuum stability and the reproducibility of photocathode fabrication. Complementing this, a novel characterization system allows spatially and spectrally resolved measurements of key photocathode parameters, such as quantum efficiency (QE), mean transverse energy (MTE), reflectance, and lifetime. Crucially, all measurements are performed within a single compact setup, without moving the sample, preserving ultrahigh vacuum conditions. The spectral resolved measurement of the reflectance allows the investigation of the color. Photocathode colorimetry may provide valuable insights into material homogeneity and aging. A Na–K–Sb photocathode was grown using the triple evaporation method, achieving an initial QE of 5.5% at 520 nm. The photocathode was characterized over 2 months, and MTE measurements were performed with two different methods. A dataset with spectral response, reflectance, and colorimetry data was recorded. Together, the triple evaporation growth and the characterization system mark a significant advancement in optimizing photocathodes with exceptional performance, paving the way for brighter and more stable electron sources for next-generation accelerator facilities.