| Negative electron affinity gallium arsenide photocathode has been developed rapidly in recent decades, because of its excellent performance.At present, gallium arsenide (GaAs) photocathodes can be gained by several typical activation techniques. But these processes are semi-quantitative and semi-empirical, the internal mechanism of activation technique of GaAs photocathodes is not very clear; the activation processes are complete by skilled operators. These manners of activation consume a large amount of manpower, and the quality and repeatability of activation will not be a good guarantee.Just because of the reasons mentioned above, this dissertation combining national project deeply explores the mechanism of activation and automatic control of activation technique. Automatic control research of GaAs photocathodes activation technique is studied. The system that can activate GaAs photocathodes intelligently is designed, and this system can improve the quality of activation.The development of GaAs photocathode is discussed in this dissertation. The theory of activation technique of GaAs photocathode is studied in detail. Through the analysis of existing surface model of GaAs phtocathode, a reasonable model is established. Use this model can explain the mechanism of activation successfully.The system that can activate GaAs photocathodes intelligently is developed. The whole structure of the system and data acquisition modules is designed and developed.The algorithm of automatic control of GaAs photocathode activation technique is designed. In this process of activation, photocurrent and vacuum can be acquired. With the change of photocurrent, the current of Cs source and O source can be automatic controlled. The algorithm is achieved by Visual C++ programming.Finally, the experiments of GaAs activation have been done many times, with the system and the software which can automatically activate the photocathode. The sensitivity of GaAs photocathode has acquired higher numerical value. |
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