中文摘要：

作为未来高平均功率、高亮度电子源的重要材料之一，负电子亲和势砷化镓（NEA-GaAs）光阴极发射的电子束亮度一直以来都是国际上的研究热点。热发射度是电子束能够实现的发射度下限，测量热发射度有利于确定注入器能否提供高亮度的电子束。本文理论计算了NEA-GaAs光阴极热发射度数值范围，并基于中国工程物理研究院自由电子激光相干强太赫兹源（FEL-THz）装置，在28fC的极低电荷量下，采用螺线管扫描法初步测量了NEA-GaAs光阴极的热发射度。结果显示，NEA-GaAs光阴极的热发射度为（0．603±0．002）μm／mm。

英文摘要：

As one of the most important high average power electron source materials, the high brightness negative electron affinity （NEA） gallium arsenide （GaAs） photo- cathode hecomes a researcher focus nowadays. The thermal emittance is the lower limit of emittance, and its measurement is of great importance to determine the brightness that an injector can provide. In this paper, based on the terahertz free electron laser （FEL-THz） facility in China Academy of Engineering Physics, some efforts were made to calculate and measure the thermal emittance of NEA-GaAs photocathode. Under ultra-low charge of 28 fC NEA-GaAs photocathode, the thermal emittance is （0. 603± 0. 002） μm/mm by the solenoid scan method.