中文摘要：

利用X射线光电子能谱（XPS）仪对激活后的GaAs真空电子源进行了随时间衰减变化的XPS分析,分析发现了电子源阴极表面各元素百分含量随时间的变化,揭示了杂质气体吸附造成的偶极矩方向的改变是电子源灵敏度显著下降的主要原因.基于上述结论,通过分析真空系统中杂质气体的吸附过程,推导并得到了GaAs电子源衰减模型.该模型从理论上揭示了GaAs电子源的指数衰减规律以及寿命与真空度的反比关系,与实验现象完全一致.

英文摘要：

The degradation of activated GaAs vacuum electron source as a function of time has been investigated by using X-ray photoelectron spectroscopy （ XPS）. We found that the cathode surface element content changes with time and the significant decrease in sensitivity of electron source is mainly due to the change of dipole direction caused by the adsorption of harmful gases on the cathode surface. Based on the above results,we deduced the degradation model of GaAs electron source through analyzing the adsorption process of harmful gases on the surface in vacuum system. The model reveals the exponential degradation rule of GaAs electron sources and the inverse relationship between lifetime and pressure. The theoretical results are in full agreement with the experimental fact.