Tungsten Thermionic Emission as a Gauge for Low Pressures of Cesium Vapor

Heated metal filaments under electric fields and low pressures of alkali metal gaseject electrons by thermionic emission as a function of the pressure of the gas and thetemperature of the filament. To explore this process in a program to develop large-area alkali metal photocathodes, we have designed and built a gauge following thestudies of Taylor and Langmuir. We present proof-of-principle measurements ofthe thermionic emission of a tungsten filament in cesium vapor. We describe a secondgeneration design that corrects flaws in the first gauge.