Method for optimizing photo cathode photo-response

A method for optimizing the photo-response of a photocathode having a gallium-arsenide layer and a cesium-oxide surface coating includes the steps of overcesiating the photocathode, sealing it in a vacuum tube and baking the assembly in an oven. The photo-response of the photocathode is measured while it is baked, such measurements comprising an input to a microprocessor which controls the baking process by varying the temperature and/or time of baking. The rate of increase of photo-response due to heating and optimizing the photo-response attributable to the cesium-oxide coating is determined by utilizing a formula which relates temperature and photo-response and permits room temperature photo-response to be projected from a measurement taken during the baking process. When the rate of increase shows a characteristic diminishing pattern, the photo-response has been maximized and the baking is terminated.