Improved activation technique for preparing high-efficiency GaAs photocathodes

In order to replace an uncontrollable gaseous oxygen source and obtain the required computer-controlled evaporation flow, two types of solid oxygen dispensers composed of silver oxide powder and barium peroxide powder are employed to prepare GaAs photocathodes. The experimental results show that the barium peroxide-based dispenser can release oxygen more effectively and deliver better photoemission performance than the silver oxide-based one. For the silver oxide-based dispenser with a long first warm-up time, an improved activation technique is proposed to avoid the Cs over-saturation and achieve the desired symmetry of photocurrent curve shape. This effective activation technique based on current-driven cesium and oxygen sources can facilitate the realization of automatic activation technology.