光阴极本征发射度离线测量装置研制

Background] Photocathode intrinsic emittance represents the lower limit of emittance achievable by photocathode electron sources. Developing photocathodes with low intrinsic emittance is critical for advancing applications such as free-electron lasers and ultrafast electron diffraction. Conventional methods for measuring photocathode intrinsic emittance rely on large-scale accelerator facilities, which are unsuitable for rapid measurement and process optimization in laboratory environments. [Purpose] This study aims to develop an offline intrinsic emittance measurement system for the optimization of photocathode process parameters. [Methods] Based on the free-space drift principle, an intrinsic emittance measurement system was designed and constructed. The measurement principle used in this system was presented in detail. The system is compatible with photocathode preparation facility, enabling offline characterization of intrinsic emittance. Using this system, the cesium telluride (CsTe) photocathode prepared by the photocathode preparation facility was measured and analyzed. [Results and Conclusions] The measurement results show that the intrinsic emittance of the cesium telluride (CsTe) photocathode is 0.592 mmmrad/mm, which is consistent with the measurement results of cesium telluride photocathodes reported. The measurement results of the intrinsic emittance under different bias voltages between the anode and the cathode are in good agreement with the theoretical values, indicating the reliability of the measurement results.