Kelvin probe studies of cesium telluride photocathode for AWA photoinjector

Cesium telluride is an important photocathode as an electron source for particle accelerators. It has a relatively high quantum efficiency ( > 1%), is sufficiently robust in a photoinjector, and has a long lifetime. This photocathode is grown in-house for a new Argonne Wakefield Accelerator (AWA) beamline to produce high charge per bunch ( ≈ 50 nC ) in a long bunch train. Here, we present a study of the work function of cesium telluride photocathode using the Kelvin probe technique. The study includes an investigation of the correlation between the quantum efficiency and the work function, the effect of photocathode aging, the effect of UV exposure on the work function, and the evolution of the work function during and after photocathode rejuvenation via heating.