Automated Fabrication Techniques For Dual-alkali Photocathodes In Large-area MCP-PMTs

Large-area micro-channel plate photomultiplier tubes(MCP-PMT)based on K₂CsSb photocathodes are core devices applied in the detection of neutrinos and cosmic rays.In order to realize large-scale production of MCP-PMT,it is necessary to improve the preparation efficiency of K₂CsSb photocathode.This paper focuses on the preparation process of K₂CsSb,and studies the automatic preparation technology of K₂CsSb.In this paper,the development of K₂CsSb photocathode and its preparation and monitoring methods are introduced,and the significance of automatic cathode preparation technology for cathode materials and large-scale production of MCP-PMT is clarified.Then,the design scheme of centralized control system for automatic cathode preparation is proposed,and the hardware part of the centralized control system is completed.It consists of central workstation,network switch and cathode preparation monitoring system.The server is used to realize the automatic preparation of cathodes,the client is used to realize the centralized control of multiple devices,and the LAN communication part is used for the data transmission between the software server and the client.Through the establishment of LAN,the network communication between central workstation and 24 cathode preparation monitoring systems is realized.Then,based on the design scheme of central control system and Visual Studio 2008 as the software development platform,the operation software of central control system is developed.The software consists of server,client and LAN communication part.Through the LAN communication,the centralized display and storage of cathode process data and equipment information are carried out,and the remote centralized control of 24 cathode preparation monitoring systems is realized.After that,the reflectivity of K₂CsSb cathode surface and the thickness of the cathode film are studied by using the theory of thin-film optical filters,combined with the research results and cathode manual preparation process,an automatic cathode preparation process suitable for computer program control is proposed,and the automatic preparation of K₂CsSb photocathode is verified by using the centralized control system.The experimental results show that the average quantum efficiency of K₂CsSb photocathode prepared by the automatic cathode preparation process is 34.76%,which is 1.3percentage points higher than that prepared by manual preparation process;the stability of the automatic cathode preparation process is good,and the repeatability is better than 10%.