GaAs光电阴极在进行Cs-O激活前．激活层表面必须达到原子级洁净。最常用且最有效的洁净方法是高温热清洗法。然而．在热清洗过程中对处在真空系统中的光电阴极表面温度进行精确测量却是非常困难的。本文采用四极质谱仪对GaAs光电阴极激活前的热清洗过程进行分析．确定了最佳的热清洗温度及热清洗工艺，较好地解决了GaAs光电阴极激活前的热清洗工艺问题。

The surface of the active layer of GaAs photocathode must reach the atomically clean surface before Cs-O activeness.The most effective method,which is used quite often,is the hight-temperature thermal cleaning one.It is very difficult to measure precisely the surface temperature of a photocathode in a vacuum system during the thermal cleaning. This paper discusses how to use a quadrupole mass spectroscope to analyzed the whole process of thermal cleaning before the activeness of GaAs photocathode,thus the temperature and technique of the optimal thermacleaning is determine.The problem for the thermal cleaning technique taken before GaAs photocathode activeness is well rolved.