The factors determining the stability of photocathodes containing alkali metals are discussed. If the necessary precautions are taken during the formation process, excellent shelf life performance can be obtained. By contrast, the stability in operation may be limited by several factors. The effects of cathode material, formation process, tube geometry, and other variables on the stability are discussed.
A. H. Sommer, "Stability of Photocathodes," Appl. Opt. 12, 90-92 (1973)