真空铟焊的负电子亲和势砷化镓光阴极实验研究

Experimental studies on NEA GaAs photocathode with vacuum indium soldering

大功率激光加载会使负电子亲和势(NEA)砷化镓(GaAs)光阴极的温度迅速升高,较高的温度对NEA GaAs光阴极的激活层造成了破坏,从而使其量子效率迅速下降。探索了基于FEL-THz装置的NEA GaAs光阴极的真空铟焊工艺,搭建了GaAs真空铟焊平台,并进行了真空铟焊后的GaAs光阴极激光与束流加载实验。研究表明,真空铟焊使GaAs与金属阴极托之间形成了紧密连接,增强了阴极与阴极托之间的热传导,减缓了阴极的温升速率,并在数瓦平均功率激光加载时将注入器中NEA GaAs光阴极的工作寿命提高了一个量级以上。

The temperature rise, caused by high power laser, would destroy the activation layer of the NEA GaAs photo cathode. In this paper, the temperature rise is studied theoretically and experimentally. With some theoretical analysis, the ther mal 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.