Thermal Emittance Measurement of Negative Electron Affinity Gallium Arsenide Photocathode

As one of the most important high average power electron source materials, the high brightness negative electron affinity (NEA) gallium arsenide (GaAs) photocathode becomes 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.