Experimental studies on NEA GaAs photocathode with vacuum indium soldering

The temperature rise, caused by high power laser, would destroy the activation layer of the NEA GaAs photocathode. In this paper, the temperature rise is studied theoretically and experimentally. With some theoretical analysis, the thermal transfer between the NEA wafer and the puck is proved as the most important factors that affect the temperature. To the thermal transfer, the GaAs vacuum indium soldering chamber is built and the vacuum soldering technology is explored. Some comparative experiments with and without indium soldering are also presented in this paper. The results, both in the atmosphere and in vacuum, indicate that indium provides effective thermal contact between the GaAs cathode and the puck, enhancing the thermal transfer and slowing down the temperature rise. These studies increase the operational lifetime of NEA GaAs illuminated by several-watt laser more than 20 times eventually.